Whole wafer coating method and edge emitting laser

Abstract

The invention relates to the technical field of semiconductor photoelectronics, in particular to a whole wafer coating method and an edge emitting laser, and the method comprises the following steps: uniformly smearing photoresist on the surface of a wafer, processing the photoresist, and manufacturing an etching window; etching a side wall through the etching window; arranging an optical film on the surface of the side wall; and removing the photoresist on the surface of the wafer. On the premise that the wafer is not scratched, the side wall of the wafer is etched, and the side wall is subjected to optical coating, so that the whole wafer is coated, a large amount of equipment, clamps, materials and labor cost are saved in the manufacturing process, and the method has a very remarkable effect on reducing the cost of an optical chip.

Description

Technical Field

[0001] The invention relates to the field of semiconductor optoelectronic technology, and in particular to a whole-wafer coating method and an edge-emitting laser. Background Art

[0002] With the technological advancement of optical chips, optical devices, and optical modules in the optical communication industry, in order to cope with the huge pressure brought by the future massive data and high-speed computing requirements, manufacturing costs have always been the target of industry development. An ordinary optical module is composed of optical devices, circuit chips, circuit boards, and optical structural parts, among which optical devices account for more than 70% of the cost of optical modules. The core of optical devices is the optical chip. Taking the mid-range optical module as an example, the current 10G optical communication chip accounts for more than 50% of the cost of the optical module. With the further improvement of the optical module rate in the future, this proportion will increase.

[0003] In order to solve the problem of data traffic explosion, data center operators must increase the number of super-large data centers. The construction of data centers is mainly based on distributed feedback lasers (DFB). Due to the rapid development of data centers, optical module products need to be upgraded every 3-4 years on average. Optical communication chips are the core components of optical modules. The upgrade of optical module transmission rate forces the update and iteration of optical communication chip products. Due to the huge demand and fast iteration rate, the manufacturing cost of optical chips needs to continue to decline.

[0004] The manufacturing cost of optical chips mainly consists of two parts. The first part is the cost of the substrate epitaxial wafer, which mainly includes the expenses on equipment such as Metal-Organic Chemical Vapor Deposition (MOCVD) and Electron Beam Lithography (EBL). The second part is the processing cost of the epitaxial wafer, which mainly includes photolithography, etching, film growth, gold plating, thinning, scratching, striping, end coating, cleavage, testing and sorting, and aging testing.

[0005] In the traditional optical chip manufacturing process, due to the particularity of edge-emitting laser chips such as distributed feedback lasers or electro-absorption modulated lasers (EML), the tape-out process cannot be completed entirely on the wafer. Because the two resonant cavity surfaces of the edge-emitting laser are hidden in the substrate structure, the substrate structure needs to be split into bars to expose the light-emitting surface and the backlight surface, and then the bars are vertically erected and placed with a special coating fixture, and then the bars are sent to the coating machine for anti-reflection coating (AR) and high-reflection coating (HR).

[0006] In this step, due to the extremely small size of the bar, whether it is machine-mounted or manual-mounted, it will cause considerable production loss to the bar, and the sophisticated coating fixtures and accompanying bars are also huge expenses in the production process.

[0007] In view of this, overcoming the defects of the prior art is an urgent problem to be solved in the field of this technology. Summary of the invention

[0008] The technical problem to be solved by the present invention is that the bars formed by machine or manual means when the substrate structure is split will result in large production losses during the coating process, and the sophisticated coating fixtures and accompanying bars will cause high costs.

[0009] In order to solve the above problems, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for coating a whole wafer, comprising:

[0011] Evenly apply photoresist on the surface of the wafer, process the photoresist, and make an etching window;

[0012] Etching a side wall through the etching window;

[0013] Arranging an optical film on the surface of the side wall;

[0014] Remove the photoresist from the wafer surface.

[0015] Preferably, the step of uniformly applying photoresist on the surface of the wafer and processing the photoresist to produce an etching window specifically includes:

[0016] Clean impurities on the wafer surface and pre-bake the wafer;

[0017] Apply photoresist evenly on the surface of the wafer;

[0018] Pre-baking the photoresist;

[0019] A mask is placed on the photoresist, and an electron beam is used for exposure. A developer is used to dissolve the photoresist after the exposure operation to obtain the etching window.

[0020] Preferably, etching the sidewalls through etching windows specifically includes:

[0021] Methane and hydrogen are used as etching gases to bombard the wafer at the etching window to etch out the side wall, wherein the flow rate of methane is 30±1Sccm, the flow rate of hydrogen is 20±1Sccm, the RF power of the etching equipment is 50±5W, and the etching depth of the wafer surface is 2±0.2μm.

[0022] Preferably, the side wall is one of a backlight surface or a light emitting surface, and the optical film is provided on the surface of the side wall, specifically comprising:

[0023] An anti-reflection optical film is arranged on the light-emitting surface, and a high-reflection optical film is arranged on the backlight surface;

[0024] The anti-reflection optical film comprises an aluminum oxide layer and a titanium oxide layer which are stacked; and the high-reflection optical film comprises an aluminum oxide layer, a titanium oxide layer, an aluminum oxide layer and a titanium oxide layer which are stacked.

[0025] Preferably, the aluminum oxide layer is prepared by:

[0026] Using trimethylaluminum as a precursor and an oxygen source as a raw material, the trimethylaluminum and the oxygen source are introduced into a reaction chamber;

[0027] The oxygen source is ionized to generate -OH groups, and trimethylaluminum is reacted with the -OH groups on the wafer surface to saturation to generate new surface functional groups;

[0028] reacting the oxygen source with the generated surface functional groups to form an aluminum oxide film on the wafer surface;

[0029] Introduce inert gas into the reaction chamber to purge the wafer surface;

[0030] The aluminum oxide layer including multiple aluminum oxide films is obtained by cyclic operation.

[0031] Preferably, the oxygen source is pure water, the fixed deposition temperature is 85°C ± 2°C, and the process pressure is 0.15 ± 0.002 Torr;

[0032] The carrier gas flow rate of trimethylaluminum is 50±1 Sccm, and the pulse time is 0.2±0.02s;

[0033] The carrier gas flow rate of the oxygen source is 100±2 Sccm, the pulse time is 0.3±0.02 s, and the duration of the purge is 10±2 s.

[0034] Preferably, the titanium oxide layer is prepared by:

[0035] Using titanium tetrachloride as a precursor and an oxygen source as a raw material, the titanium tetrachloride is introduced into a reaction chamber;

[0036] Passing an oxygen source into the reaction chamber so that the oxygen source reacts with titanium tetrachloride to form a titanium oxide film;

[0037] Introduce inert gas into the reaction chamber to purge the wafer surface;

[0038] The titanium oxide layer including multiple titanium oxide thin films is obtained by cyclic operation.

[0039] Preferably, the oxygen source is one of pure water or oxygen, the fixed deposition temperature is 85°C ± 2°C, and the process pressure is 0.15 ± 0.002 Torr;

[0040] The carrier gas flow rate of the titanium tetrachloride is 110±1 Sccm, and the pulse time is 0.2±0.02s;

[0041] The carrier gas flow rate of the oxygen source is 150±1 Sccm, the pulse time is 0.2±0.02 s, and the duration of the purge is 4±1 s.

[0042] Preferably, the thickness of the aluminum oxide layer of the anti-reflection optical film is 31.02±0.02 nm; the thickness of the titanium oxide layer of the anti-reflection optical film is 25.61±0.02 nm;

[0043] The thickness of the aluminum oxide layer of the high-reflection optical film is 101.59±0.02 nm; the thickness of the titanium oxide layer of the anti-reflection optical film is 69.39±0.02 nm.

[0044] In a second aspect, the present invention provides an edge emitting laser, wherein the edge emitting laser is obtained by cleaving a wafer, and the wafer is coated using the whole wafer coating method as described in the first aspect.

[0045] The beneficial effect of the present invention is that, by etching the side wall on the end face of the edge emitting laser in the wafer without scratching the wafer, and optically coating the side wall, the entire wafer can be coated. In this way, the end face coating of the edge emitting laser can be completed without scratching the wafer into bars, thereby saving a large amount of equipment, fixtures, materials and labor costs in the manufacturing process, and having a very significant effect on reducing the cost of optical chips.

[0046] Furthermore, the chip end face is coated using atomic layer deposition technology (ALD). Compared with other coating methods, the film thickness of the ALD coating method is more uniform, which improves the manufacturing yield. In addition, the improvement of the manufacturing process saves a lot of manpower and material costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0048] Figure 1 It is a schematic diagram of the overall process flow of a whole-wafer coating method provided by an embodiment of the present invention;

[0049] Figure 2 is a schematic diagram of step 10 of a whole-wafer coating method provided by an embodiment of the present invention;

[0050] Figure 3 is a schematic diagram of step 11 of a whole-wafer coating method provided by an embodiment of the present invention;

[0051] Figure 4 It is a specific flow chart of step 10 of a whole-wafer coating method provided by an embodiment of the present invention;

[0052] Figure 5 It is a schematic diagram of a mask plate of a whole-wafer coating method provided by an embodiment of the present invention;

[0053] Figure 6 It is a schematic diagram of a whole-wafer coating method using wet etching provided by an embodiment of the present invention;

[0054] Figure 7 It is a schematic diagram of a whole-wafer coating method using dry etching provided by an embodiment of the present invention;

[0055] Figure 8 It is a schematic diagram of the principle and equipment of a whole-wafer coating method using reactive ion etching provided by an embodiment of the present invention;

[0056] Fig. 9 It is a schematic diagram of the principle of reactive ion etching of a whole-wafer coating method provided by an embodiment of the present invention;

[0057] Fig.10It is a schematic flow chart of a method for forming an aluminum oxide layer in a whole-wafer coating method provided by an embodiment of the present invention;

[0058] Fig.11 It is a schematic flow chart of a method for generating a titanium oxide thin film layer in a whole-wafer coating method provided by an embodiment of the present invention;

[0059] Fig.12 It is a schematic diagram of wafer thinning in a whole-wafer coating method provided by an embodiment of the present invention;

[0060] Fig.13 It is a schematic diagram of a wafer scribing mechanism of a whole wafer coating method provided by an embodiment of the present invention;

[0061] Fig.14 It is a schematic diagram of wafer cleavage positions in a whole-wafer coating method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0063] In the description of the present invention, the orientations or positional relationships indicated by terms such as "inside", "outside", "up", "down", "top", and "bottom" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention rather than requiring that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0064] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0065] Embodiment 1:

[0066] Embodiment 1 of the present invention provides a method for coating a whole wafer, such as Figure 1 As shown, including:

[0067] In step 10, photoresist is evenly applied on the surface of the wafer, and the photoresist is processed to produce an etching window.

[0068] Specifically, Figure 2As shown, the type of the photoresist can be a positive photoresist. In the photolithography process, after the positive photoresist coating is exposed and developed, the unexposed part can be retained to form a photoresist of the image. Positive photoresist has the characteristics of good chemical resistance, good adhesion, high resolution, etc., and is therefore widely used in the photolithography process. The type of the photoresist can also be a negative photoresist, which is not specifically limited in this embodiment.

[0069] In step 11, a sidewall is etched through the etching window.

[0070] like Figure 3 As shown, in an actual application scenario, a groove is etched through the etching window, and the sidewalls are two side edges of the groove perpendicular to the bottom surface. At the same time, in one embodiment, the etching method used is reactive ion etching.

[0071] In step 12, an optical film is disposed on the surface of the side wall.

[0072] In one embodiment, the technical method for setting the optical film on the side wall is atomic deposition technology, which is a special chemical vapor deposition technology. It is a method of forming a thin film by alternately passing a gas phase precursor pulse into a reaction chamber and causing a chemical adsorption reaction on the surface of a deposition substrate. It has excellent three-dimensional conformality, large-area uniformity, and precise single-layer film thickness control. In actual application scenarios, setting an optical film on the surface of the side wall means using atomic deposition technology to cover the surface of the groove etched through the etching window with an optical film, but its main purpose is to cover the side wall with an optical film.

[0073] In step 13, the photoresist on the surface of the wafer is removed.

[0074] Specifically, before ALD film growth, a layer of photoresist is already provided on the surface that does not need to be coated. After the film growth, an organic solvent is used to dissolve the photoresist, and the optical film grown on the surface of the photoresist can also be removed together.

[0075] By etching the side walls of the wafer without scratching it and performing optical coating on the side walls, the entire wafer can be coated, saving a lot of equipment, fixtures, materials and labor costs in the manufacturing process, which has a very significant effect on reducing the cost of optical chips. Furthermore, atomic deposition technology is used to coat the end faces of the chip. Compared with other coating methods, the film thickness of the ALD coating method is more uniform and consistent, which improves the manufacturing yield, and the improvement of the manufacturing process saves a lot of labor and material costs.

[0076] In order to further illustrate the complete solution of the embodiment of the present invention, the details of the above steps are described in detail below.

[0077] In the above step 10, before obtaining the etching window, the wafer needs to be inspected, pre-baked, coated, pre-baked and photolithography exposed in five steps, as shown in detail. Figure 4 As shown, the process of uniformly applying photoresist on the surface of the wafer and processing the photoresist to produce an etching window specifically includes:

[0078] In step 100, impurities on the surface of the wafer are cleaned and the wafer is pre-baked.

[0079] The purpose of cleaning the wafer is that the operation before the wafer is coated may introduce surface impurities, so microscopic inspection is required. If the wafer is dirty, a specific process cleaning is required to ensure the cleanliness of the wafer surface.

[0080] The purpose of pre-baking is to avoid the introduction of water vapor or contaminants on the surface of the wafer during the process of cleaning the wafer, which will cause the wafer to have weak adhesion during the coating process, thereby causing the process pattern to fall off easily. In one embodiment, the pre-baking temperature is 50°C ± 1°C and the time is 30 ± 1 minutes. Due to the large number of variables in the actual experimental scenario, the time and temperature of pre-baking are not specifically limited in the embodiments of the present invention.

[0081] In step 101, photoresist is evenly coated on the surface of a wafer.

[0082] Specifically, in actual application scenarios, there are two methods for applying photoresist on the surface of the wafer, namely, the spin coating method and the automatic spraying method. Among them, the spin coating method is the most widely used method. The silicon wafer is placed in the container for the wafer on the coating machine, and the computer is used to set the program so that the silicon wafer automatically enters the coating tray for spraying, and then the coated silicon wafer is sent to the pre-drying machine with a conveyor belt; the automatic spraying method is to place the silicon wafer in the container for the wafer on the coating machine, and the computer is used to set the program so that the silicon wafer automatically enters the coating tray for spraying, and then the conveyor belt is used to send the coated silicon wafer to the pre-drying machine. Both of these coating methods are well known to those skilled in the art and will not be repeated here.

[0083] In step 102, the photoresist is pre-baked.

[0084] Specifically, after the photoresist is uniformly coated on the wafer surface, it is necessary to heat and bake the photoresist to promote the volatilization and drying of the photoresist, and increase the adhesion and wear resistance between the photoresist and the wafer. Among them, the pre-baking temperature and time of the photoresist specifically depend on the product requirements and process conditions of the photoresist. Under normal circumstances, the pre-baking temperature and time vary according to the type of photoresist used. In the embodiment of the present invention, the pre-baking temperature and time are not specifically limited. For thicker films, the pre-baking temperature rise rate should be slow, otherwise the surface will dry too quickly, and the internal solvent will not have time to volatilize, which will easily cause the film to bubble and produce pinholes, resulting in poor contact and floating glue during development or corrosion. The higher the pre-baking temperature and the longer the time, the better the adhesion between the photoresist and the substrate, but if the pre-baking time is too long, it will cause excessive volatilization of the sensitizer; if the temperature is too high, the photoresist will be warped and hardened, resulting in unclean development, reduced resolution of the graphics, and reduced corrosion resistance.

[0085] In step 103, a mask is placed on the photoresist, an electron beam is used for exposure, and a developer is used to dissolve the photoresist after the exposure operation to obtain the etching window.

[0086] When the photoresist is a positive photoresist, a mask is placed on the photoresist and an electron beam is used for exposure. The part not covered by the mask is dissolved by the developer to obtain the etching window.

[0087] It is worth mentioning that placing the mask is an important step in pattern transfer and requires alignment with the positioning mark. If the pattern is not aligned, there will be overlap and misalignment of the pattern, such as Figure 5 As shown, it is a schematic diagram of the mask. Among them, the photoresist needs to be evenly coated with a suitable thickness, so that in the later etching process, after the light-emitting surface is etched, there is still residual photoresist to protect other surfaces of the wafer.

[0088] When etching the sidewall through the etching window, in the prior art, there are mainly wet etching and dry etching. Since wet etching will form undercutting (such as Figure 6 As shown in the figure), the shape of the light-emitting surface is irregular, which greatly affects the light-emitting efficiency. In severe cases, it will cause catastrophic damage to the end mirror surface. Therefore, wet etching is not used. In dry etching, we use reactive ion etching, which has very good anisotropy and selectivity and can etch a regular and smooth light-emitting surface (as shown in the figure). Figure 7 As shown), a good environment can be formed for the later ALD coating. Specifically, the etching of the side wall through the etching window specifically includes:

[0089] Methane and hydrogen are used as etching gases to bombard the wafer at the etching window to etch out the side wall, wherein the flow rate of methane is 30±1Sccm, the flow rate of hydrogen is 20±1Sccm, the RF power of the etching equipment is 50±5W, and the etching depth of the wafer surface is 2±0.2μm.

[0090] The principle is that, Figure 8 As shown, first, methane (CH4) and hydrogen (H2) are introduced into the etching equipment, usually through a pipe or a gas generator. Then, these gases are ionized into ions in the ionization chamber of the etching equipment. This process requires the irradiation of high-energy electrons or laser beams to decompose the gas molecules into ions and free electrons; then, these ions are accelerated to a high-energy state and bombarded with the surface of the wafer to be etched in the form of an ion beam. This process is called ion beam etching. During ion beam etching, ions collide with atoms on the surface of the wafer (such as Fig. 9 As shown in the figure, the atoms on the surface are driven out and volatile substances are formed. This process will lead to different degrees and types of etching depending on the gas composition and the energy of the ions. Finally, the part etched away from the wafer surface will form grooves or patterns, which depends on the energy and direction of the ion beam used.

[0091] Normally, the entire vacuum wall of the reactive ion etching machine is grounded as the anode, the cathode is the power electrode, and the grounded shield on the side of the cathode can prevent the power electrode from being sputtered; the substrate to be etched is placed on the power electrode, and the etching gas fills the entire reaction chamber according to a certain working pressure and matching ratio. For the etching gas in the reaction chamber, a high-frequency electric field greater than the critical value of gas breakdown is added. Under the strong electromagnetic effect, the random collisions between the stray electrons accelerated by the high-frequency electric field and the gas molecules or atoms become inelastic collisions, which continuously excite or ionize the gas molecules. This violent collision causes ionization and recombination. When the process of electron generation and disappearance reaches equilibrium, the discharge energy can continue to be maintained. The ions, electrons and free radicals (free atoms, molecules or atomic groups) generated by the inelastic collision are also called plasma. They have strong chemical activity and can react chemically with the atoms on the surface of the etched sample to form volatile substances, thereby achieving the purpose of etching the surface of the sample. At the same time, since the direction of the electric field near the cathode is perpendicular to the cathode surface, high-energy ions are vertically shot toward the sample surface under a certain working pressure for physical bombardment, making the reactive ion etching have good anisotropy.

[0092] In a wafer used to manufacture edge-emitting lasers, the side wall is one of a backlight surface or a light-emitting surface, and an optical film is arranged on the surface of the side wall, specifically including: an anti-reflection optical film is arranged on the light-emitting surface, and a high-reflection optical film is arranged on the backlight surface; the anti-reflection optical film is also called an anti-reflection coating, which can reduce the reflection of light and allow more light energy to pass through; the high-reflection optical film is also called a high-reflection coating, which can enhance the reflection of light and enable light energy to be effectively utilized.

[0093] In the present embodiment, the grooves obtained when etching the side walls on the wafer surface specifically include grooves for setting the anti-reflection optical film and grooves for setting the high-reflection optical film according to the position distribution of the grooves; wherein the grooves for setting the anti-reflection optical film and the grooves for setting the high-reflection optical film are alternately distributed; the two side walls of the grooves for setting the anti-reflection optical film are both light emitting surfaces, and the two side walls of the grooves for setting the high-reflection optical film are both backlight surfaces.

[0094] In this embodiment, the grooves corresponding to the light-emitting surface and the grooves corresponding to the backlight surface are made in advance through step 10 and step 11, and then the light-emitting surface and the backlight surface are coated respectively. In the coating process, if the light-emitting surface is coated, it is necessary to apply photoresist on the surface of the backlight surface, that is, on the part that does not need coating, and after the light-emitting surface is coated, an organic solvent is used to dissolve the photoresist; if the backlight surface is coated, it is necessary to apply photoresist on the surface of the light-emitting surface, that is, apply photoresist on the part that does not need coating, and after the backlight surface is coated, an organic solvent is used to dissolve the photoresist. Since the film coated on the light-emitting surface and the backlight surface is an inorganic substance, and the photoresist is an organic substance, the previously coated film will not be dissolved in the process of using an organic solvent to dissolve the photoresist.

[0095] The anti-reflection optical film comprises an aluminum oxide layer and a titanium oxide layer stacked together; the high-reflection optical film comprises an aluminum oxide layer, a titanium oxide layer, an aluminum oxide layer and a titanium oxide layer stacked together. Specifically, the thickness of the aluminum oxide layer of the anti-reflection optical film is 31.02±0.02nm; the thickness of the titanium oxide layer of the anti-reflection optical film is 25.61±0.02nm; the thickness of the aluminum oxide layer of the high-reflection optical film is 101.59±0.02nm; and the thickness of the titanium oxide layer of the anti-reflection optical film is 69.39±0.02nm.

[0096] Specifically, aluminum oxide (Al2O3) is used as the first layer because it has a strong affinity to the chip surface, has good adhesion, and aluminum oxide itself is a dense oxide film, which has unparalleled advantages in isolating water vapor compared to other films. Titanium oxide (TiO2) has the characteristics of high refractive index and low absorption rate, which can improve the utilization rate of light; and titanium oxide is a stable material with excellent chemical and physical properties. It can maintain stable performance in harsh environments such as high temperature and high pressure, has good compatibility with the wafer surface, will not cause damage or pollution to the wafer surface, and can form good adhesion with the wafer surface; in addition, titanium oxide has good corrosion resistance, which can effectively protect the wafer surface from corrosion and extend the service life of the wafer.

[0097] In the coating process of edge-emitting lasers, electron beam evaporation or magnetron sputtering is often used to complete the coating of the resonant cavity optical film. However, since both technologies belong to physical deposition methods, this deposition method has a disadvantage that during the deposition process, the deposition rate on the front of the sample is different from the deposition rate on the side wall of the sample. Generally speaking, this ratio is 2:1 or 3:1, and the ratio is difficult to control in the actual process. In addition, when the sample is rotated, the thickness of the left and right side walls will also be inconsistent. Therefore, in an embodiment of the present invention, atomic deposition technology is used to coat the light-emitting surface and the backlight surface.

[0098] According to the above content, if Fig.10 As shown, the preparation method of the aluminum oxide layer is:

[0099] In step 20, trimethylaluminum is used as a precursor and an oxygen source is used as a raw material, and trimethylaluminum and the oxygen source are introduced into a reaction chamber.

[0100] In step 21, an oxygen source is ionized to generate -OH groups, and trimethylaluminum is reacted with the -OH groups on the wafer surface to saturation to generate new surface functional groups.

[0101] Specifically, the -OH group is generated by ionization of pure water.

[0102] In step 22, an oxygen source is reacted with the generated surface functional groups to form an aluminum oxide film on the surface of the wafer.

[0103] In step 23, an inert gas is introduced into the reaction chamber to purge the surface of the wafer.

[0104] Wherein, the inert gas is nitrogen or argon. Due to the high cost of argon, nitrogen is mostly used for purging in experiments for cost considerations. In the process of preparing aluminum oxide film by ALD, each time trimethylaluminum and water react to generate aluminum oxide, it is necessary to use an inert gas for purging to remove impurities and unreacted substances in the reaction chamber to ensure the purity and consistency of each reaction, thereby ensuring the quality and thickness of the aluminum oxide film. Specifically, the step of purging with an inert gas is usually at the end of each ALD cycle, by passing an inert gas to remove impurities and unreacted substances in the reaction chamber. This process helps to keep the reaction chamber clean to ensure the smooth progress of the next cycle.

[0105] In step 24, the process is cyclically operated to obtain an aluminum oxide layer including multiple aluminum oxide films.

[0106] Specifically, when coating the light-emitting surface, steps 20 to 23 need to be cycled about 310 times, and the thickness is 31.02 nm; when coating the backlight surface, steps 20 to 23 need to be cycled about 1016 times, and the thickness is 101.59 nm. The more cycles are repeated, the thicker the aluminum oxide layer is obtained. The specific number of cycles is determined according to actual needs and is not specifically limited in the embodiments of the present invention.

[0107] According to the coating process carried out according to the above process steps, the film growth rate of aluminum oxide is 0.1nm / Cycle, and the specific parameters in the process are as follows: the oxygen source uses pure water, the fixed deposition temperature is 85℃±2℃, and the process pressure is 0.15±0.002Torr; the carrier gas flow rate of the trimethylaluminum is 50±1Sccm, and the pulse time is 0.2±0.02s; the carrier gas flow rate of the oxygen source is 100±2Sccm, the pulse time is 0.3±0.02s, and the purge time is 10±2s.

[0108] After the aluminum oxide layer is plated on the wafer surface, a titanium oxide layer needs to be placed on top of the aluminum oxide layer. Fig.11 As shown, specifically, the preparation method of the titanium oxide layer is:

[0109] In step 30, titanium tetrachloride is used as a precursor and an oxygen source is used as a raw material, and the titanium tetrachloride is introduced into a reaction chamber.

[0110] In step 31, an oxygen source is introduced into a reaction chamber to react with titanium tetrachloride to form a titanium oxide film.

[0111] In step 32, an inert gas is introduced into the reaction chamber to purge the surface of the wafer.

[0112] In step 33, the process is cyclically operated to obtain a titanium oxide layer including a plurality of titanium oxide thin films.

[0113] Specifically, when coating the light-emitting surface, steps 30 to 33 need to be cycled about 128 times, and the thickness is 25.61 nm; when coating the backlight surface, steps 30 to 33 need to be cycled about 347 times, and the thickness is 69.39 nm. The more cycles are repeated, the thicker the titanium oxide layer is obtained. The specific number of cycles is determined according to actual needs and is not specifically limited in the embodiments of the present invention.

[0114] According to the coating process carried out according to the above process steps, the film growth rate of titanium oxide is 0.2nm / Cycle, and the specific parameters in the process are as follows: the oxygen source uses one of pure water or oxygen, the fixed deposition temperature is 85℃±2℃, and the process pressure is 0.15±0.002Torr; the carrier gas flow rate of the titanium tetrachloride is 110±1Sccm, and the pulse time is 0.2±0.02s; the carrier gas flow rate of the oxygen source is 150±1Sccm, the pulse time is 0.2±0.02s, and the purge time is 4±1s.

[0115] Finally, by debonding, the entire wafer with the optical film coated on the side walls can be obtained, and then a thinning process is carried out to prepare the front and back metal electrodes, and finally a scratching and cleavage process is performed to obtain the final finished chip.

[0116] Among them, Fig.12 As shown, the thinning process is to thin the bottom of the wafer. The purpose of thinning is to reduce the thickness of the wafer so that it is more in line with specific application requirements; improve thermal stability. Through the thinning process, the thermal stress of the wafer during the heat treatment process can be reduced, and its thermal stability can be improved, which helps to reduce deformation or cracking caused by temperature changes. Problems such as; enhance the surface quality of the wafer. The thinning process can remove defects and impurities on the surface of the wafer caused by processing or coating, improve the surface quality, and help improve the appearance and performance of the wafer; optimize optical performance. For some optical applications, such as optoelectronic devices, optical sensors, etc., it is necessary to accurately control the thickness and surface quality of the wafer. The thinning process can optimize the optical performance of the wafer and improve its reflection, transmission or interference effects; at the same time, the thinning process can also make the wafer thinner, easier to transport and use, and further reduce costs. In the process of etching the wafer, the wafer needs to have a certain thickness to ensure that the wafer will not break during the etching process. Therefore, before obtaining the final finished chip, the wafer needs to be thinned.

[0117] The demarcation is as follows: Fig.13 As shown in FIG. 1 , the coated wafer is cleaved along the dotted line to form small chips, with the two opposite long sides of the chip being the light-emitting surface and the backlight surface. Fig.14 As shown, the grooves obtained when etching the side walls on the wafer surface, according to the position distribution of the grooves, specifically include grooves for setting the anti-reflection optical film, and grooves for setting the high-reflection optical film; wherein, the grooves for setting the anti-reflection optical film and the grooves for setting the high-reflection optical film are alternately distributed; the two side walls of the grooves for setting the anti-reflection optical film are both light-emitting surfaces, and the two side walls of the grooves for setting the high-reflection optical film are both backlight surfaces, and when performing cleavage, cleavage is performed along the position indicated by the dotted line.

[0118] In addition to the solutions mentioned above, an embodiment of the present invention further provides an edge emitting laser, which is obtained by cleaving a wafer, and the wafer is coated using the whole wafer coating method as described in the above solution.

[0119] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for coating a whole wafer, characterized in that: include: Evenly apply photoresist on the surface of the wafer, process the photoresist, and make an etching window; Etching a side wall through the etching window; Arranging an optical film on the surface of the side wall; Remove the photoresist from the wafer surface.

2. The whole wafer coating method according to claim 1, characterized in that: The method comprises: uniformly applying photoresist on the surface of the wafer, processing the photoresist, and making an etching window, specifically comprising: Clean impurities on the wafer surface and pre-bake the wafer; Apply photoresist evenly on the surface of the wafer; Pre-baking the photoresist; A mask is placed on the photoresist, and an electron beam is used for exposure. A developer is used to dissolve the photoresist after the exposure operation to obtain the etching window.

3. The whole wafer coating method according to claim 1, characterized in that: The etching of the sidewall through the etching window specifically includes: Methane and hydrogen are used as etching gases to bombard the wafer at the etching window to etch out the side wall, wherein the flow rate of methane is 30±1Sccm, the flow rate of hydrogen is 20±1Sccm, the RF power of the etching equipment is 50±5W, and the etching depth of the wafer surface is 2±0.2μm.

4. The whole wafer coating method according to claim 1, characterized in that: The side wall is one of a backlight surface and a light emitting surface, and the optical film is provided on the surface of the side wall, specifically comprising: An anti-reflection optical film is arranged on the light-emitting surface, and a high-reflection optical film is arranged on the backlight surface; The anti-reflection optical film comprises an aluminum oxide layer and a titanium oxide layer which are stacked; and the high-reflection optical film comprises an aluminum oxide layer, a titanium oxide layer, an aluminum oxide layer and a titanium oxide layer which are stacked.

5. The whole wafer coating method according to claim 4, characterized in that: The preparation method of the aluminum oxide layer is: Using trimethylaluminum as a precursor and an oxygen source as a raw material, the trimethylaluminum and the oxygen source are introduced into a reaction chamber; The oxygen source is ionized to generate -OH groups, and trimethylaluminum is reacted with the -OH groups on the wafer surface to saturation to generate new surface functional groups; reacting the oxygen source with the generated surface functional groups to form an aluminum oxide film on the wafer surface; Introduce inert gas into the reaction chamber to purge the wafer surface; The aluminum oxide layer including multiple aluminum oxide films is obtained by cyclic operation.

6. The whole wafer coating method according to claim 5, characterized in that: The oxygen source is pure water, the fixed deposition temperature is 85°C ± 2°C, and the process pressure is 0.15 ± 0.002 Torr; The carrier gas flow rate of trimethylaluminum is 50±1 Sccm, and the pulse time is 0.2±0.02s; The carrier gas flow rate of the oxygen source is 100±2 Sccm, the pulse time is 0.3±0.02 s, and the duration of the purge is 10±2 s.

7. The whole wafer coating method according to claim 4, characterized in that: The preparation method of the titanium oxide layer is: Using titanium tetrachloride as a precursor and an oxygen source as a raw material, the titanium tetrachloride is introduced into a reaction chamber; Passing an oxygen source into the reaction chamber so that the oxygen source reacts with titanium tetrachloride to form a titanium oxide film; Introduce inert gas into the reaction chamber to purge the wafer surface; The titanium oxide layer including multiple titanium oxide thin films is obtained by cyclic operation.

8. The whole wafer coating method according to claim 7, characterized in that: The oxygen source is one of pure water or oxygen, the fixed deposition temperature is 85°C ± 2°C, and the process pressure is 0.15 ± 0.002 Torr; The carrier gas flow rate of the titanium tetrachloride is 110±1 Sccm, and the pulse time is 0.2±0.02s; The carrier gas flow rate of the oxygen source is 150±1 Sccm, the pulse time is 0.2±0.02 s, and the duration of the purge is 4±1 s.

9. The whole wafer coating method according to claim 4, characterized in that: The thickness of the aluminum oxide layer of the anti-reflection optical film is 31.02±0.02 nm; the thickness of the titanium oxide layer of the anti-reflection optical film is 25.61±0.02 nm; The thickness of the aluminum oxide layer of the high-reflection optical film is 101.59±0.02 nm; the thickness of the titanium oxide layer of the anti-reflection optical film is 69.39±0.02 nm.

10. An edge emitting laser, characterized in that: The edge-emitting laser is obtained by cleaving a wafer, and the wafer is coated by the whole-wafer coating method as described in any one of claims 1 to 9.

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