Preparation method of antireflection film of semiconductor laser

Abstract

The invention provides a preparation method of an antireflection film of a semiconductor laser, and belongs to the technical field of semiconductor lasers. The problem that a film layer falls off in an existing anti-reflection film preparation process is solved. Comprising the following steps: pretreatment cleaning before bar coating: vacuumizing a chamber of reaction magnetic control equipment to a vacuum degree of 10 <-6 > Torr grade, turning on a heating lamp to heat the chamber to a set temperature, starting an ion source, introducing a proper amount of plasma gas into the ion source, introducing a proper amount of plasma gas into the chamber to enable the vacuum degree of the chamber to reach a 10 <-3 > Torr grade, and then cleaning; in the process steps of plating the silicon nitride thin film and the aluminum oxide thin film, a chamber is kept at a certain temperature, and then the vacuum degree of the chamber is reduced during film plating; and the performance of the laser is stably improved while the production yield of the semiconductor laser is improved.

Description

Technical Field

[0001] The invention provides a method for preparing a semiconductor laser anti-reflection film, belonging to the technical field of semiconductor lasers. Background Art

[0002] As we all know, the three elements for the operation of semiconductor lasers are excited matter, population inversion and stable resonant cavity.

[0003] The most widely used semiconductor laser at present is the semiconductor laser composed of a Fabry-Perot resonant cavity, that is, an anti-reflection film and a high-reflection film are respectively coated on the front and back cavity surfaces of the laser to form a resonant cavity.

[0004] Cavity surface coating technology is extremely critical, especially in high-power semiconductor lasers. The high optical power density, large defect density, dislocations and other defects at the cavity surface will produce surface light absorption and non-radiative recombination. Light absorption and non-radiative recombination will intensify with increasing temperature, forming a positive feedback process, thereby leading to the occurrence of optical catastrophes.

[0005] After the cavity surface film layer is prepared, it needs to be packaged and tested for optical performance. Currently, high-power semiconductor lasers are widely used in microchannel linear array packaging technology. The packaging process places increasingly stringent requirements on the optical film on the end face of the bar. It needs to be ultrasonically cleaned with various organic solvents and maintain its original properties. The test performance and reliability after packaging cannot be affected. Therefore, it is necessary to grow a film layer with high adhesion, high wear resistance, and high corrosion resistance.

[0006] After the GaAs epitaxial wafer has completed the P-side and N-side processes, it is cleaved into bars of fixed length, and then the anti-reflection film and high-reflection film are prepared. The current anti-reflection film coating process uses reactive magnetic control preparation to complete the three processes of cleaning the bar end face, growing the protective film and the anti-reflection film layer in the chamber, as follows: 1. Cleaning: Place the bar into the coating fixture and put it into the vacuum chamber of the reaction magnetron equipment, and evacuate to 2.0×10 -6 Torr, the ion source was started with a power of 300 W, 8 sccm of argon was introduced into the ion source, 55 sccm of argon was introduced into the chamber, and the chamber vacuum was 1.1×10 -3 Torr, cleaning time 150s. The main purpose of cleaning is to remove the oxides formed in the air on the cavity surface after cleavage, to avoid the instability of laser optical performance and optical catastrophe caused by the presence of oxides after coating.

[0007] 2. Silicon nitride film: The protective film is mainly composed of Si3N4, which is a commonly used dielectric film material. Silicon nitride film has good optical properties, passivation properties and water vapor penetration resistance. It is also used as an anti-reflection film, and plays the role of surface passivation and internal passivation. At present, the preparation of Si3N4 film also uses reactive magnetron equipment. After the cleaning process is completed, the chamber is evacuated to 2.0×10 -6 Torr, start the Si target gun, its power is 700W, 30sccm argon is introduced into the Si target gun, start the ion source, its power is 250W, 3sccm argon and 11sccm nitrogen are introduced into the ion source, the deposition rate is controlled to be 2Å / s, the growth thickness is 20nm, and the chamber vacuum is 1.7×10 -3 Torr.

[0008] 3. Aluminum oxide film: It has a wide range of applications in the optical and microelectronic fields due to its excellent optical properties, extremely high mechanical strength and hardness, good transparency and insulation, wear resistance, corrosion resistance, high resistance to laser damage and chemical inertness. The preparation of Al2O3 film also uses reactive magnetron equipment. After the silicon nitride film is prepared, the chamber is evacuated to 2.0×10 -6 Torr, start the Al target gun, its power is 700W, 90sccm argon is introduced into the Al target gun, start the ion source, its power is 400W, 15sccm argon and 13sccm oxygen are introduced into the ion source, the deposition rate is controlled to be 3.5Å / s, the growth thickness is 80nm, and the chamber vacuum is 1.8×10 -3 Torr.

[0009] At present, the packaging technology of high-power semiconductor lasers is constantly improving, and the bar has to withstand greater tests than before. For example, during the microchannel linear array packaging process, the bar cavity surface may be rubbed with flux, and chloroform ultrasonic cleaning is required. During the ultrasonic cleaning process, due to the poor adhesion between the film layer and the bar, the film layer may fall off, affecting the performance and reliability of the laser. Therefore, it is necessary to adjust the film layer process, reduce the film layer stress, enhance adhesion, and improve the stability of the laser. Summary of the invention

[0010] In view of the problems existing in the existing anti-reflection film production process, the present invention proposes a method for preparing a semiconductor laser anti-reflection film, which is optimized on the basis of the existing process and is used to solve the problem of film shedding in the subsequent packaging and device preparation process, thereby improving the production yield and stably improving the performance of the laser.

[0011] The technical solution adopted by the present invention is: a method for preparing a semiconductor laser anti-reflection film, comprising the following steps: S1. Cleave the large wafer into strips of fixed length and remove them from the blue film for later use; S2. After cleaning the coating fixture, place the bar into the coating fixture; S3, placing the coating fixture into the vacuum chamber of the reaction magnetron device and starting the coating operation; S4, anti-reflection coating: S4.1. Pretreatment and cleaning of the strips before coating: Evacuate the chamber of the reaction magnetron equipment to 10 -6 The vacuum degree of the chamber reaches 10 Torr level. The heating lamp is turned on to heat the chamber to the set temperature. The ion source is started, and an appropriate amount of plasma gas is introduced into the ion source. Then, an appropriate amount of plasma gas is introduced into the chamber to make the vacuum degree of the chamber reach 10 -3 Torr level, then clean; S4.2, Silicon nitride film deposition: the chamber is evacuated to 10 -6 Torr level, and when the chamber temperature reaches the set temperature, start the Si target gun, start the ion source, introduce appropriate amount of plasma gas and nitrogen into the ion source, and then introduce appropriate amount of plasma gas into the chamber to make the chamber vacuum reach 10 -3 Torr level, so that the deposition rate of silicon nitride film is maintained within the set range and a certain thickness is deposited; S4.3, aluminum oxide film coating: the chamber is evacuated to 10 -6 Torr, and when the chamber temperature reaches the set temperature, start the Al target gun, start the ion source, introduce appropriate amounts of plasma gas and oxygen into the ion source, and then introduce appropriate amounts of plasma gas into the chamber to make the chamber vacuum reach 10 -3 Torr level, so that the deposition rate of aluminum oxide film is kept within the set range and a certain thickness is deposited; S5, high reflective film on the rear cavity; S6. Cool down the chamber and release the air, take out the coating fixture, remove the bar, and perform packaging testing.

[0012] Furthermore, in steps S4.1, S4.2 and S4.3, the set temperature in the chamber is 100-120°C.

[0013] Furthermore, the set temperature in the chamber in steps S4.1, S4.2 and S4.3 is 100°C.

[0014] Furthermore, in step 4.2, the power of the Si target gun is 390-410 W, and an appropriate amount of plasma gas is introduced through the Si target gun.

[0015] Furthermore, in step 4.3, the power of the Al target gun is 690-710 W, and an appropriate amount of plasma gas is introduced through the Al target gun.

[0016] Furthermore, the plasma gas specifically uses argon and / or nitrogen.

[0017] Furthermore, before the packaging test in step S6, the bars are cleaned with an organic solvent.

[0018] Furthermore, before the packaging test in step S6, ultrasonic cleaning is performed using chloroform for a period of time, then ultrasonic cleaning is performed using alcohol for a period of time, then cleaning is performed using deionized water for a period of time, and finally drying is performed using a nitrogen gun.

[0019] The beneficial effects of the present invention compared with the prior art are as follows: 1. When the chamber is pumping the vacuum degree, the higher the vacuum limit, the slower the pumping speed. When the chamber begins to pump the vacuum limit and the chamber temperature reaches 100°C, due to the high temperature, the gas molecules attached to the inner wall of the chamber will be quickly pumped away by the molecular pump, quickly achieving high vacuum and shortening the process time.

[0020] 2. During the process of making silicon nitride film and aluminum oxide film, the chamber is always kept at 100℃. Properly increasing the chamber temperature can make the film material vapor react more violently with the cavity surface of the strip, improve the bonding force between the film layer and the cavity surface of the strip, form a denser film, and improve the refractive index of the film layer. The temperature should not be too high, which may cause large particles to condense or material decomposition, or even fogging of the film layer.

[0021] 3. When preparing the anti-reflection film, 200sccm argon is introduced when preparing the silicon nitride film, and 100sccm argon is introduced when preparing the aluminum oxide film. The purpose is to reduce the vacuum degree and reduce the target gun power to achieve the purpose of reducing the deposition rate. When the evaporation rate is low, the adsorbed atoms can fully migrate on the surface during their average residence time, and condensation can only be carried out on large condensates. The reverse evaporation is serious, so the film structure is loose. On the contrary, the deposition rate is increased, the structure is tighter, but the internal stress increases due to the increase in defects, so it is particularly critical to adjust the optimal deposition rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below in conjunction with the accompanying drawings: Figure 1 The process flow chart of preparing an antireflection film by the method of the present invention is as follows; Figure 2 It is a schematic diagram of the structure of each part of the bar; Figure 3 is a schematic diagram of depositing silicon nitride film; Figure 4 It is a schematic diagram of coating aluminum oxide film; Figure 5 This is a cleaning process flow chart; In the figure: 1 is the bar, 2 is the cavity surface, 3 is the light-emitting point, 4 is the P surface, 5 is the N surface, 6 is the silicon nitride film, and 7 is the aluminum oxide film. DETAILED DESCRIPTION

[0023] like Figures 1 to 5 As shown, the present invention provides a method for preparing a semiconductor laser anti-reflection film, which improves the existing process mentioned in the background technology, and the specific improvements are as follows: 1. Before the cleaning process of the existing process, that is, when the chamber is evacuated, the chamber is heated to 100°C and the chamber is evacuated to 2×10 -6 Torr, and then the cleaning process is carried out.

[0024] 2. When making silicon nitride film 6 by the existing process, in addition to the existing process parameters, the chamber temperature is kept unchanged at 100°C, the target gun power is reduced to 400W, and 200sccm of argon is introduced, and the chamber vacuum becomes 4.1×10 -3 Torr, the deposition rate of silicon nitride film 6 was reduced to 0.91Å / s, and the thickness remained at 20nm.

[0025] 3. When making aluminum oxide film 7 by the existing process, in addition to the existing process parameters, the chamber temperature is kept at 100°C, 100 sccm of argon is introduced, and the chamber vacuum is changed to 3.2×10 -3 Torr, the deposition rate remained basically unchanged at about 3.5Å / s, and the thickness remained at 80nm.

[0026] The process flow for preparing the improved semiconductor laser anti-reflection film of the present invention is as follows: Figure 1 As shown, the specific implementation steps are as follows: S1, cleave the large wafer into strips 1 of fixed length, remove them from the blue film and set them aside for use; the structure of the strips 1 is as follows Figure 2 As shown, it includes a cavity surface 2, a P surface 4 (epitaxial surface) and an N surface 5 (substrate surface), wherein the side where the cavity surface 2 contacts the P surface 4 is a front cavity, on which an anti-reflection film is coated, and the side where the cavity surface 2 contacts the N surface 5 is a back cavity, on which a high-reflection film is coated, and the P surface 4 is spaced apart with light-emitting points 3.

[0027] S2, after cleaning the coating fixture, put the bar 1 into the coating fixture; S3, placing the coating fixture into the vacuum chamber of the reaction magnetron device and starting the coating operation; S4, anti-reflection coating: S4.1. Pretreatment and cleaning of strip 1 before coating: Evacuate the chamber of the reaction magnetron device to 10 -6 The vacuum degree of the chamber reaches 10 Torr level. The heating lamp is turned on to heat the chamber to the set temperature. The ion source is started, and an appropriate amount of plasma gas is introduced into the ion source. Then, an appropriate amount of plasma gas is introduced into the chamber to make the vacuum degree of the chamber reach 10 -3 Torr level, then clean; S4.2, silicon nitride film deposition 6: the chamber is evacuated to 10 -6Torr level, and when the chamber temperature reaches the set temperature, start the Si target gun, start the ion source, introduce appropriate amount of plasma gas and nitrogen into the ion source, and then introduce appropriate amount of plasma gas into the chamber to make the chamber vacuum reach 10 -3 Torr level, so that the deposition rate of the silicon nitride film 6 is maintained within a set range and a certain thickness is deposited; S4.3, aluminum oxide film coating 7: the chamber is evacuated to 10 -6 Torr, and when the chamber temperature reaches the set temperature, start the Al target gun, start the ion source, introduce appropriate amounts of plasma gas and oxygen into the ion source, and then introduce appropriate amounts of plasma gas into the chamber to make the chamber vacuum reach 10 -3 Torr level, so that the deposition rate of the aluminum oxide film 7 is kept within the set range and a certain thickness is deposited; S5, high reflective film on the rear cavity; S6. Cool down the chamber and release the air, take out the coating fixture, remove the bar 1, and perform packaging test.

[0028] Since the bar 1 of the high-power laser will be contaminated with flux during the packaging process (to make the bar 1 more wet with the solder, avoid the formation of voids and reduce the reliability of the device), in order to remove the flux contaminated on the cavity surface 2 and avoid introducing new dirt at the light-emitting point 3, a Figure 5 The strip 1 is cleaned by the organic solvent cleaning steps shown, specifically, first using chloroform ultrasonic cleaning for 15 minutes, then using alcohol ultrasonic cleaning for 10 minutes, then using deionized water to clean for 2 minutes, and finally blowing dry with a nitrogen gun.

[0029] The process flow of the present invention is described below based on specific embodiments.

[0030] Example 1 S1. Cleave the large wafer into strips 1 of fixed length and remove them from the blue film for later use.

[0031] S2. After cleaning the coating fixture, manually install the bar 1 into the coating fixture.

[0032] S3, placing the coating fixture into the vacuum chamber of the reaction magnetron equipment, and starting the coating operation. The entire time from cleavage to placing in the vacuum chamber does not exceed 20 minutes.

[0033] S4, anti-reflection coating: S4.1. Pretreatment and cleaning of strip 1 before coating: evacuate the chamber of the reaction magnetron device to a vacuum of 2.0×10 -6 Torr, turn on the heating lamp to heat the chamber to 100°C, start the ion source with a power of 300W, introduce 8sccm argon into the ion source and 55sccm argon into the chamber, and the chamber vacuum will become 1.1×10 -3Torr, cleaning time 150s.

[0034] S4.2, silicon nitride film deposition 6: the chamber is evacuated to 2.0×10 -6 Torr, the chamber temperature is 100℃, the Si target gun is started, its power is 400W, 30sccm argon is introduced into the Si target gun, the ion source is started, its power is 250W, 3sccm argon and 11sccm nitrogen are introduced into the ion source, 200sccm argon is introduced into the chamber, and the chamber vacuum becomes 4.1×10 -3 Torr, the deposition rate of silicon nitride film 6 was reduced to 0.91Å / s, and the thickness was kept at 20nm. Figure 3 .

[0035] S4.3, Al2O3 film coating 7: the chamber is evacuated to 2.0×10 -6 Torr, the chamber temperature was maintained at 100°C, the Al target gun was started with a power of 700W, 90sccm of argon was introduced into the Al target gun, the ion source was started with a power of 400W, 15sccm of argon and 13sccm of oxygen were introduced into the ion source, 100sccm of argon was introduced into the chamber, and the chamber vacuum became 3.2×10 -3 Torr, the deposition rate remains basically unchanged, about 3.5Å / s, and the thickness remains at 80nm. See the attached Figure 4 .

[0036] S5, high reflective film is applied to the rear cavity.

[0037] S6. Cool down the chamber and release the air, take out the coating fixture, remove the bar 1, and perform packaging test.

[0038] Example 2 S1. Cleave the large wafer into strips 1 of fixed length and remove them from the blue film for later use.

[0039] S2. After cleaning the coating fixture, manually install the bar 1 into the coating fixture.

[0040] S3, placing the coating fixture into the vacuum chamber of the reaction magnetron equipment, and starting the coating operation. The entire time from cleavage to placing in the vacuum chamber does not exceed 20 minutes.

[0041] S4, anti-reflection coating: S4.1. Pretreatment and cleaning of strip 1 before coating: evacuate the chamber of the reaction magnetron device to a vacuum of 2.0×10 -6 Torr, turn on the heating lamp to heat the chamber to 120°C, start the ion source with a power of 300W, introduce 8sccm argon into the ion source and 55sccm argon into the chamber, and the chamber vacuum will become 1.1×10 -3 Torr, cleaning time 150s.

[0042] S4.2, silicon nitride film deposition 6: the chamber is evacuated to 2.0×10 -6 Torr, the chamber temperature is 120℃, the Si target gun is started, its power is 400W, 30sccm argon is introduced into the Si target gun, the ion source is started, its power is 250W, 3sccm argon and 11sccm nitrogen are introduced into the ion source, 200sccm argon is introduced into the chamber, and the chamber vacuum becomes 4.1×10 -3 Torr, the deposition rate of silicon nitride film 6 was reduced to 0.91Å / s, and the thickness was kept at 20nm. Figure 3 .

[0043] S4.3, Al2O3 film coating 7: the chamber is evacuated to 2.0×10 -6 Torr, the chamber temperature was maintained at 120°C, the Al target gun was started with a power of 700W, 90sccm of argon was introduced into the Al target gun, the ion source was started with a power of 400W, 15sccm of argon and 13sccm of oxygen were introduced into the ion source, 100sccm of argon was introduced into the chamber, and the chamber vacuum became 3.2×10 -3 Torr, the deposition rate remains basically unchanged, about 3.5Å / s, and the thickness remains at 80nm. See the attached Figure 4 .

[0044] S5, high reflective film is applied to the rear cavity.

[0045] S6. Cool down the chamber and release the air, take out the coating fixture, remove the bar 1, and perform packaging test.

[0046] The method for preparing the semiconductor laser anti-reflection film provided by the present invention can improve the bonding force between the film layer and the cavity surface 2, and can solve the problem of the film layer falling off during ultrasonic cleaning using a high-frequency ultrasonic machine due to the contamination of the cavity surface 2 with flux in the subsequent packaging process and the need to be immersed in organic solvents such as chloroform and ethanol. The entire process time is only increased by 10-20 minutes compared to before, and the optical performance and reliability of the laser packaged are not affected, providing more opportunities for the development of laser packaging technology.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a semiconductor laser anti-reflection film, characterized in that: The following steps are involved: S1. Cleave the large wafer into strips of fixed length and remove them from the blue film for later use; S2. After cleaning the coating fixture, place the bar into the coating fixture; S3, placing the coating fixture into the vacuum chamber of the reaction magnetron device and starting the coating operation; S4, anti-reflection coating: S4.

1. Pretreatment and cleaning of the strips before coating: Evacuate the chamber of the reaction magnetron equipment to 10 -6 The vacuum degree of the chamber reaches 10 Torr level. The heating lamp is turned on to heat the chamber to the set temperature. The ion source is started, and the plasma gas is introduced into the ion source. Then, the plasma gas is introduced into the chamber to make the vacuum degree of the chamber reach 10 -3 Torr level, then clean; S4.2, Silicon nitride film deposition: the chamber is evacuated to 10 -6 Torr level, and when the chamber temperature reaches the set temperature, start the Si target gun, start the ion source, introduce plasma gas and nitrogen into the ion source, and then introduce plasma gas into the chamber to make the chamber vacuum reach 10 -3 Torr level, and then deposit silicon nitride film; S4.3, aluminum oxide film coating: the chamber is evacuated to 10 -6 Torr, and when the chamber temperature reaches the set temperature, start the Al target gun, start the ion source, introduce plasma gas and oxygen into the ion source, and then introduce plasma gas into the chamber to make the chamber vacuum reach 10 -3 Torr level, and then deposit aluminum oxide thin film; S5, high reflective film on the rear cavity; S6. Cool down the chamber and release the air, take out the coating fixture, remove the bar, and perform packaging testing.

2. The method for preparing a semiconductor laser anti-reflection film according to claim 1, characterized in that: The set temperature in the chamber in steps S4.1, S4.2 and S4.3 is 100-120°C.

3. The method for preparing a semiconductor laser anti-reflection film according to claim 2, characterized in that: The set temperature in the chamber in steps S4.1, S4.2 and S4.3 is 100°C.

4. The method for preparing a semiconductor laser anti-reflection film according to claim 1, characterized in that: In step 4.2, the power of the Si target gun is 390-410 W, and plasma gas is introduced into the Si target gun.

5. The method for preparing a semiconductor laser anti-reflection film according to claim 1, characterized in that: In step 4.3, the power of the Al target gun is 690-710 W, and plasma gas is introduced into the Al target gun.

6. A method for preparing a semiconductor laser anti-reflection film according to any one of claims 1 to 5, characterized in that: Argon and / or nitrogen are used as plasma gas.

7. The method for preparing a semiconductor laser anti-reflection film according to claim 6, characterized in that: Before the packaging test in step S6, the strips are cleaned with an organic solvent.

8. The method for preparing a semiconductor laser anti-reflection film according to claim 7, characterized in that: Before the packaging test in step S6, ultrasonic cleaning is first performed using chloroform, then ultrasonic cleaning is performed using alcohol, then cleaning is performed using deionized water, and finally drying is performed using a nitrogen gun.

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