VCSEL-based semiconductor laser and preparation method thereof

Abstract

The invention provides a VCSEL-based semiconductor laser and a preparation method thereof, and the semiconductor laser comprises a VCSEL chip which is provided with a light-emitting surface; the diffusion plate is cured on the light-emitting surface of the VCSEL chip; and a micro lens structure is formed on the surface of the diffusion plate and comprises micro lenses which are tightly arranged. The process of preparing the diffusion plate and the process of packaging the diffusion plate to the VCSEL wafer are combined into a whole by utilizing the upper mold and the lower mold which are mutually folded, and a plurality of independent steps in the traditional process are combined through process integration, so that the manufacturing and packaging cost is greatly saved, the production process is effectively saved, the working efficiency and the product yield are improved, and the production cost is reduced. And the light emitting angle of the semiconductor laser can be conveniently adjusted.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, in particular to a VCSEL-based semiconductor laser and a preparation method thereof. Background Art

[0002] VCSEL (Vertical-cavity Surface-emitting Laser) was initially used in the field of optical communications, such as in optical modules, and then gradually applied to 3D sensing in the field of consumer electronics, such as face recognition. In 2017, a mobile phone brand manufacturer used it in face recognition modules, and since then it has attracted a large amount of attention in the field of consumer electronics, and has begun to enter the market of mobile phones, smart door locks, sweeping robots, unmanned driving, AR / VR and other fields.

[0003] At present, when packaging products, it is generally necessary to further configure a diffuser on the surface of the VCSEL chip to ensure that the packaged product emits surface-shaped projection light while increasing the detectable spatial range. The process flow is generally as follows: after the VCSEL chip and the diffuser are independently prepared, the VCSEL chip is first fixed inside the 3D bracket during packaging, and then the diffuser is fixed to the step surface of the 3D bracket to obtain a packaged product that meets the luminous angle requirements. The problems with this packaging method are mainly reflected in: on the one hand, the cost of the 3D bracket is high; on the other hand, it is difficult to control when the diffuser is attached to the surface of the 3D bracket, which is difficult. Summary of the invention

[0004] In order to overcome the above shortcomings, the present invention provides a semiconductor laser based on VCSEL and a preparation method thereof, which effectively solves the problems of complex process, high cost and great difficulty of existing semiconductor lasers.

[0005] The technical solution provided by the present invention is:

[0006] In one aspect, the present invention provides a semiconductor laser based on VCSEL, comprising:

[0007] VCSEL chip, with a light-emitting surface;

[0008] A diffusion plate is solidified on the light-emitting surface of the VCSEL chip; a microlens structure is formed on the surface of the diffusion plate, and the microlens structure includes closely arranged microlenses.

[0009] On the other hand, the present invention provides a method for preparing a semiconductor laser based on VCSEL, comprising:

[0010] Providing a lower mold adapted to the upper mold of the laminator, wherein the lower mold includes a mold bottom plate, and a closely arranged micro-arc groove structure is formed in the mold bottom plate;

[0011] A wafer with a flip-chip VCSEL chip formed on its surface is fixed on an upper mold of a laminator;

[0012] forming a layer of release agent in the lower mold of the laminating machine;

[0013] Filling a certain amount of polymer material on the surface of the release agent;

[0014] The upper mold and the lower mold of the laminating machine are molded together, and the polymer material is initially solidified;

[0015] The wafer with the polymer material cured on the surface is taken out from the laminator, and the polymer material is further cured to form a diffusion plate on the light-emitting surface of the VCSEL chip, and a microlens structure is formed on the surface of the diffusion plate;

[0016] The wafer is cut to obtain a single semiconductor laser.

[0017] The VCSEL-based semiconductor laser and the preparation method thereof provided by the present invention utilize an upper mold and a lower mold that match each other to combine the process of preparing a diffusion plate and the process of packaging the diffusion plate onto a VCSEL wafer into one, so that the diffusion plate is directly formed on the surface of the VCSEL wafer during the curing process. Through process integration, multiple independent steps in the traditional process are combined, which not only greatly saves the manufacturing and packaging costs, but also effectively saves the production process; the diffusion plate is formed on the surface of the VCSEL chip in an integrated molding manner, and there is no need to use adhesive glue to fix the diffusion plate, which reduces the risks caused by weak bonding, glue aging, etc., greatly improves reliability, is conducive to improving work efficiency and product yield, and is convenient for adjusting the light output angle of the semiconductor laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the semiconductor laser in the present invention;

[0019] Figure 2 It is a schematic diagram of the process of preparing a semiconductor laser based on VCSEL in the present invention. DETAILED DESCRIPTION

[0020] In order to more clearly illustrate the implementation cases of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings and other implementation methods can be obtained based on these drawings without creative work.

[0021] The first embodiment of the present invention is a VCSEL-based semiconductor laser, comprising: a VCSEL chip having a light-emitting surface; a diffusion plate solidified on the light-emitting surface of the VCSEL chip; a microlens structure formed on the surface of the diffusion plate, the microlens structure comprising closely arranged micro lenses.

[0022] VCSEL is generally top-emitting. To meet the needs of different field of view (FOV), VCSEL is usually assembled with lenses of certain specifications according to actual product requirements after the mounting and wire bonding processes to diffuse the light so as to emit it more evenly into the external space. In this embodiment, the upper mold and the lower mold are matched with each other, the VCSEL wafer is placed in the upper mold, the polymer material for preparing the diffusion plate is injected into the lower mold, and the polymer material is cured after the upper mold and the lower mold are combined, so that the diffusion plate is directly formed on the surface of the VCSEL wafer during the curing process, without the need for re-packaging. After curing, the diffusion plate between the VCSEL chips is cut to obtain a single semiconductor laser with a diffusion plate. The diffusion plate is integrally formed on the light-emitting surface of the VCSEL chip, which effectively reduces the difficulty of the packaging process; in addition, in the lower mold A closely arranged hemispherical groove structure is also etched in the tool, and a corresponding microlens structure is formed on the surface of the cured diffusion plate away from the VCSEL chip. The microlens structure includes closely arranged microlenses, and the structure of the microlenses is convex, which matches the VCSEL chip in the VCSEL wafer. After the light from the VCSEL chip is shaped by the microlens structure in the diffusion plate, it can be uniformly diverged in a larger range (including horizontal and vertical ranges). Therefore, the microlens structure configured on the surface of the diffusion plate can better adjust the light output angle of the semiconductor laser device. In other embodiments, concave, partially convex, partially concave microlenses can also be formed. This embodiment does not limit this, and the design can be made according to the actual needs of the product.

[0023] The diffusion plate is made of polymer materials, and can be made of one or more of epoxy resin, silicone resin, PPA, PET, and acrylic. Figure 1As shown, the diffuser plate has a microlens structure on the surface that includes closely arranged microlenses, and each microlens is a hemispherical lens. The size and arrangement of each microlens are sufficient to satisfy the horizontal field of view angle range of 15° to 180° and the vertical field of view angle range of 15° to 180°. In other words, after the microlens structure of the diffuser plate processes the light from the VCSEL chip, it can achieve a field of view of 15° to 180° in the horizontal direction, that is, on the basis of the main light, it can also diverge 7.5° to 90° to the left and right sides respectively. It can also achieve a field of view of 15° to 180° in the vertical direction, that is, on the basis of the main light, it can also diverge 7.5° to 90° to the upper and lower sides respectively. The range of the field of view angle can also be determined according to actual application requirements. Figure 1 As shown in (a) in FIG. 1 , the microlenses in the microlens structure are uniform and arranged in an array; Figure 1 As shown in (b), the sizes of the microlenses in the microlens structure are different and they are closely arranged together. In other embodiments, in the diffuser plate structure formed, in addition to forming the microlens structure, a diffuser structure of a certain thickness can be formed under the microlens structure, that is, between the microlens structure and the VCSEL chip according to application requirements.

[0024] Another embodiment of the present invention is a method for preparing a semiconductor laser based on VCSEL, comprising:

[0025] S10 provides a lower mold adapted to the upper mold of the laminator, wherein the lower mold includes a mold bottom plate, and a closely arranged micro-arc groove structure is formed in the mold bottom plate.

[0026] The function of the lower mold is to form a diffusion plate on the surface of the VCSEL wafer, so a lower mold matching the diffusion plate is provided in advance. In the lower mold, the area of ​​the mold bottom plate is equal to or greater than the area of ​​the VCSEL wafer, and at least a closely arranged hemispherical groove structure is formed on the mold bottom plate. Since the groove structure determines the shape of the microlens structure after the subsequent diffusion plate is cured, it plays a decisive role in the light output angle of the final semiconductor laser. Therefore, the size, size, shape, arrangement, etc. of each groove structure in the mold bottom plate should be determined in advance according to product requirements; as in one example, the closely arranged groove structure in the mold bottom plate is a hemispherical shape with the same size and shape, and after the diffusion plate is cured, a uniform and array-arranged microlens structure can be obtained. In another example, the closely arranged groove structure in the mold bottom plate is an ellipse of different sizes. In other embodiments, if a diffusion structure of a certain thickness is formed below the microlens structure, that is, between the microlens structure and the VCSEL chip, a mold sidewall of a corresponding thickness may also be formed on the side of the mold base plate in the lower mold, that is, the lower mold is composed of the mold base plate and the mold sidewall surrounding the edge of the mold base plate, and when the lower mold is closed with the upper mold, the side with the mold sidewall is closed with the upper mold.

[0027] S20 fixes a wafer with a flip-chip VCSEL chip formed on a surface thereof on an upper mold of a laminator.

[0028] After plasma cleaning, the wafer with the flip-chip VCSEL chip is placed on the upper mold of the laminator by vacuum adsorption, with the light-emitting surface of the VCSEL chip facing outward. Since this embodiment is prepared for VCSEL wafers, the overall size and shape of the upper mold and the lower mold of the laminator should be designed according to the shape and size of the VCSEL wafer, and should be at least equal to or larger than the VCSEL wafer, so as to facilitate accommodating the VCSEL wafer.

[0029] S30 forms a layer of release agent in the lower mold of the laminator.

[0030] Since the polymer material used to prepare the diffuser plate is generally easy to bond with other materials, in order to facilitate the subsequent demoulding of the diffuser plate, a layer of release agent is formed on the working surface of the lower mold (i.e., the side with the micro-arc groove structure) in advance. The release agent itself does not bond with the surface of the lower mold, and can help the diffuser plate to be completely separated from the lower mold without damaging the microlens structure on the surface. The selection of the release agent material is determined according to the materials of the diffuser plate and the lower mold, and can achieve the purpose of peeling the cured diffuser plate from the lower mold. The use of the release agent can make the surface of the diffuser plate smooth and complete on the one hand, and it is also helpful to protect the lower mold from damage on the other hand. The release agent is evenly covered on the entire surface of the lower mold, usually by spraying or brushing: the spraying method can cover quickly and evenly, which is particularly suitable for molds with complex shapes; brushing is more suitable for larger or flatter mold areas. Regardless of which method is used, it must be ensured that there is no missing area of ​​the release agent on the surface of the lower mold, otherwise it may cause local adhesion when the diffuser plate is demoulded later. When the lower mold includes a mold bottom plate and a mold side wall surrounding the edge of the mold bottom plate, a release agent should be formed on both the surface of the mold bottom plate and the inner surface of the mold side wall.

[0031] S40 fills a certain amount of polymer material on the surface of the release agent.

[0032] The polymer material used can be one or more of epoxy resin, silicone resin, PPA, PET, and acrylic. In this process, it is only necessary to fill a certain amount of polymer material on the surface of the lower mold. The amount of polymer material should be sufficient to ensure that it can completely fill every corner of the lower mold, especially to cover the micro-arc groove structure on the bottom plate of the mold. These groove structures are often small in size and complex in shape, so it is necessary to ensure that the material is filled in place to avoid any gaps or defects; when the upper and lower molds are closed, the other surface of the polymer material should be in close contact with the light-emitting surface of the VCSEL wafer, so that the diffusion plate can be directly formed on the surface of the VCSEL wafer during the curing process.

[0033] S50 closes the upper mold and the lower mold of the laminator and performs preliminary curing of the polymer material.

[0034] The purpose of preliminary curing is to shape the diffusion plate so that it can be separated from the lower mold. The curing conditions are determined by the properties of the polymer material. For example, when the material used is epoxy resin, it is baked at 200°C for 3 minutes for preliminary curing. At the same time, in the preliminary curing process, in addition to temperature and time, it is also necessary to adjust the parameters of the laminating machine, such as heating rate, cooling rate, vacuum degree, vacuum time, etc. to ensure the shape and quality of the diffusion plate are intact, and to avoid problems such as poor shape, bubbles, and glue cracking. In this process, by controlling the heating and cooling rates, it is possible to prevent uneven internal stress caused by rapid temperature changes, thereby avoiding shape deformation and cracking; at the same time, appropriate vacuum degree and vacuum time settings can effectively remove bubbles in the material and improve the density and appearance quality of the finished product.

[0035] S60 takes the wafer with the polymer material cured on the surface out of the laminator, and further cures the polymer material to form a diffusion plate on the light-emitting surface of the VCSEL chip.

[0036] During demolding, the upper mold is separated from the lower mold, and the initially cured diffuser plate is separated from the lower mold and formed on the surface of the VCSEL wafer; in order to completely cure the diffuser plate, after demolding from the laminator, the wafer with the polymer material cured on the surface is further cured. The curing conditions are also determined by the properties of the polymer material. For example, when the material used is epoxy resin, the wafer is placed in an oven and baked at 200°C for 1h (hour) for complete curing. The entire process of forming the diffuser plate does not require the use of glue and separate packaging, and the diffuser plate is directly cured on the surface of the VCSEL wafer. The surface of the formed diffuser plate has a microlens structure, which includes closely arranged hemispherical lenses, and the horizontal field of view of the diffuser plate ranges from 15° to 180°, and the vertical field of view ranges from 15° to 180°. In another embodiment, after the upper mold and the lower mold of the laminator are molded together and the polymer material is initially cured, the step of complete curing can be continued in the laminator; that is, after the initial curing is completed, the parameters of the laminator are adjusted to meet the conditions of complete curing, and the complete curing is directly carried out in the laminator, and then the upper mold is separated from the lower mold, the diffusion plate is separated from the lower mold, and the VCSEL wafer is separated from the upper mold, to obtain a wafer with a completely cured diffusion plate, and then the wafer is cut. Compared with the previous embodiment, this embodiment only needs to complete the entire curing process (including initial curing and complete curing) in the laminator before demolding, and there is no need to move it to an oven after demolding, which further simplifies the process.

[0037] S70 cuts the wafer into individual semiconductor lasers.

[0038] After cutting to obtain a single semiconductor laser, the single laser is sorted by optoelectronic parameters, taped and stored.

[0039] It should be noted that the above embodiments can be freely combined as needed. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention.

Claims

1. A semiconductor laser based on VCSEL, characterized in that: include: VCSEL chip, with a light-emitting surface; A diffusion plate is solidified on the light-emitting surface of the VCSEL chip; a microlens structure is formed on the surface of the diffusion plate, and the microlens structure includes closely arranged microlenses.

2. The semiconductor laser according to claim 1, characterized in that In the microlens structure, each microlens is a hemispherical lens.

3. The semiconductor laser according to claim 1 or 2, characterized in that: The horizontal viewing angle of the diffuser plate ranges from 15° to 180°, and the vertical viewing angle ranges from 15° to 180°.

4. The semiconductor laser according to claim 1 or 2, characterized in that: The diffusion plate is made of polymer material.

5. The semiconductor laser according to claim 4, characterized in that The diffusion plate is made of one or more of epoxy resin, silicone resin, PPA, PET, and acrylic.

6. A method for preparing a semiconductor laser based on VCSEL, characterized in that: include: Providing a lower mold adapted to the upper mold of the laminator, wherein the lower mold includes a mold bottom plate, and a closely arranged micro-arc groove structure is formed in the mold bottom plate; A wafer with a flip-chip VCSEL chip formed on its surface is fixed on an upper mold of a laminator; forming a layer of release agent in the lower mold of the laminating machine; Filling a certain amount of polymer material on the surface of the release agent; The upper mold and the lower mold of the laminating machine are molded together, and the polymer material is initially solidified; The wafer with the polymer material cured on the surface is taken out from the laminator, and the polymer material is further cured to form a diffusion plate on the light-emitting surface of the VCSEL chip, and a microlens structure is formed on the surface of the diffusion plate; The wafer is cut to obtain a single semiconductor laser.

7. The method for preparing a semiconductor laser according to claim 6, characterized in that: The microlens structure includes closely arranged microlenses, and each microlens is a hemispherical lens.

8. The method for preparing a semiconductor laser according to claim 6 or 7, characterized in that: The horizontal viewing angle of the diffuser plate ranges from 15° to 180°, and the vertical viewing angle ranges from 15° to 180°.

9. The semiconductor laser according to claim 6 or 7, characterized in that The diffusion plate is made of one or more of epoxy resin, silicone resin, PPA, PET, and acrylic.

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