Semiconductor laser preparation method and semiconductor laser

Abstract

The present invention discloses a method for preparing a semiconductor laser. The method comprises the steps of forming a dielectric spacer layer structure for reducing parasitic capacitance on the surface of an epitaxial substrate, and evaporating a PAD electrode on the surface of the epitaxial substrate having the dielectric spacer layer structure formed thereon; forming the dielectric spacer layer structure on the surface of the epitaxial substrate using the following process: S1, preparing a dielectric layer on the surface of the epitaxial substrate; S2, forming a photoresist mask on the surface of the dielectric layer; S3, treating the photoresist mask using a lightweight thermal reflow process so that the edge of the photoresist mask forms an arc-shaped profile; S4, etching the dielectric layer using a dry etching process with an etching selectivity of 0.8 to 1.2 to form a dielectric spacer layer structure with an arc-shaped edge profile, and removing residual photoresist. The present invention also discloses a semiconductor laser. The present invention can ensure the connectivity of PAD metal evaporation, and has a simple process and low implementation cost.

Description

Technical Field

[0001] The invention relates to a method for preparing a semiconductor laser, and belongs to the technical field of semiconductor laser manufacturing. Background Art

[0002] In the semiconductor laser manufacturing process, it is often necessary to set a dielectric pad high layer structure composed of dielectric materials such as BCB (benzocyclobutene), PI (polyimide), or SiO between the PAD electrode and the epitaxial substrate to reduce the parasitic capacitance of the laser. In the process flow, the PAD electrode is usually evaporated after the dielectric pad high layer structure process is completed. The connectivity of the PAD electrode evaporated at the edge contour of the dielectric pad high layer structure is directly affected by the contour of the dielectric pad high layer structure. If the contour of the dielectric pad high layer structure is steep, it will cause the evaporated metal to break, which will seriously affect the performance and reliability of the semiconductor laser. The preparation of the existing dielectric pad high layer structure is through exposure, baking and development conditions to obtain a mask and then form it through dry etching. This easily causes the edge contour of the dielectric pad high layer structure to be steep and sharp. Achieving a smooth edge contour of the dielectric pad high layer structure is very difficult in process debugging. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a semiconductor laser preparation method, which can obtain an ideal arc-shaped edge profile of a dielectric pad layer structure, ensure the PAD metal evaporation connectivity, and has a simple process and low implementation cost.

[0004] The present invention specifically adopts the following technical solutions to solve the above technical problems:

[0005] A method for preparing a semiconductor laser comprises the steps of forming a dielectric spacer layer structure for reducing parasitic capacitance on the surface of an epitaxial substrate, and evaporating a PAD electrode on the surface of the epitaxial substrate having the dielectric spacer layer structure formed thereon; the dielectric spacer layer structure is formed on the surface of the epitaxial substrate using the following process:

[0006] S1, preparing a dielectric layer on the surface of the epitaxial substrate;

[0007] S2, forming a photoresist mask on the surface of the dielectric layer;

[0008] S3, processing the photoresist mask using a lightweight thermal reflow process, so that the edge of the photoresist mask forms an arc-shaped profile;

[0009] S4. Etching the dielectric layer using a dry etching process with an etching selectivity ratio of 0.8 to 1.2 to form a dielectric pad layer structure with an arc-shaped edge profile, and removing residual photoresist.

[0010] Preferably, the dielectric layer material is BCB, PI, or SiO.

[0011] Preferably, the processing temperature of the lightweight thermal reflow process is within the glass transition temperature range of the photoresist used, and the processing time is 5s to 70s.

[0012] Based on the above technical solution, we can also obtain:

[0013] A semiconductor laser is prepared using the method described in any of the above technical solutions.

[0014] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0015] The present invention processes a photoresist mask based on a lightweight thermal reflow process so that the mask edge forms an arc-shaped profile, and combines a dry etching process with an etching selectivity ratio of about 1 to replicate the arc-shaped profile of the mask edge to the edge of the dielectric layer, thereby generating a dielectric cushion layer structure with an ideal arc-shaped smooth edge profile, thereby ensuring the continuity of metal evaporation at the profile edge and improving the performance and reliability of the semiconductor laser. The technical solution of the present invention is simple and easy to implement and can be realized using existing process equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figures 1 to 6 Schematic diagram of the preparation process of the dielectric cushion layer structure. DETAILED DESCRIPTION

[0017] To address the issue of the edge profile of the dielectric spacer layer structure affecting the quality of subsequent metal evaporation, the present invention solves the problem by using a lightweight thermal reflow process to process the photoresist mask so that the mask edge forms an arc-shaped profile. This is then combined with a dry etching process with an etching selectivity of approximately 1 to transplant the arc-shaped profile of the mask edge to the edge of the dielectric layer, thereby producing a dielectric spacer layer structure with an ideal arc-shaped smooth edge profile. This ensures the continuity of metal evaporation at the profile edge and improves the performance and reliability of the semiconductor laser.

[0018] The traditional thermal reflow process involves heating the developed photoresist to a temperature above its glass transition temperature, causing it to soften and deform. The reflow process can be viewed as a simple physical model: the photoresist structure attempts to deform while minimizing its specific surface area and maximizing its contact surface with the substrate. The impact of these two mechanisms on the final photoresist morphology depends on the ratio of the photoresist's viscosity to its adhesion to the substrate. When the viscosity-to-adhesion ratio is very high (corresponding to extremely poor wettability), photoresist beads will theoretically form on the substrate; however, when adhesion dominates (extremely strong adhesion), the photoresist structure will attempt to flatten onto the substrate surface. Currently, the thermal reflow process is primarily used in the fabrication of microlenses, where it creates a spherical or cylindrical photoresist profile, which is then transferred. The present invention utilizes a thermal reflow process not to create a spherical or cylindrical photoresist profile, but rather to reshape the edge of the photoresist mask, resulting in a smooth, curved shape. This function is similar to chamfering in machining. Therefore, the heat reflow process used in the present invention only needs to have a treatment temperature within the glass transition temperature range of the photoresist, rather than exceeding the glass transition temperature as required in traditional heat reflow processes. This process is referred to herein as a lightweight heat reflow process. The specific parameters of the lightweight heat reflow process vary depending on the performance parameters of the specific photoresist used. The optimal temperature and time for softening and deforming the edges of a photoresist mask of a corresponding thickness while maintaining the overall profile can be determined in advance through experimentation. The preferred treatment temperature is within the glass transition temperature range of the photoresist used, and the treatment time is 5 to 70 seconds.

[0019] To precisely transfer the arc-shaped edge of the photoresist mask pattern to the dielectric layer, the present invention uses a dry etching process with an etch selectivity of approximately 1 (0.8 to 1.2) to etch the dielectric layer. It should be noted that since the etch selectivity is approximately 1 or even lower than 1, the thickness of the photoresist mask must be sufficient to meet etching requirements.

[0020] In summary, the technical solutions proposed in the present invention are as follows:

[0021] A method for preparing a semiconductor laser comprises the steps of forming a dielectric spacer layer structure for reducing parasitic capacitance on the surface of an epitaxial substrate, and evaporating a PAD electrode on the surface of the epitaxial substrate having the dielectric spacer layer structure formed thereon; the dielectric spacer layer structure is formed on the surface of the epitaxial substrate using the following process:

[0022] S1, preparing a dielectric layer on the surface of the epitaxial substrate;

[0023] S2, forming a photoresist mask on the surface of the dielectric layer;

[0024] S3, processing the photoresist mask using a lightweight thermal reflow process, so that the edge of the photoresist mask forms an arc-shaped profile;

[0025] S4. Etching the dielectric layer using a dry etching process with an etching selectivity ratio of 0.8 to 1.2 to form a dielectric pad layer structure with an arc-shaped edge profile, and removing residual photoresist.

[0026] To facilitate public understanding, the technical solution of the present invention is described in detail below through a specific embodiment with reference to the accompanying drawings:

[0027] The semiconductor laser of this embodiment uses a 3-inch epitaxial structure wafer with a SiO protective layer deposited on the surface of the epitaxial wafer. The preparation process of its dielectric high-layer structure is as follows:

[0028] Step 1: Preparation of dielectric layer:

[0029] Coat BCB on the surface of the epitaxial wafer with a thickness of 2.4 μm to obtain the following Figure 1 The structure of the epitaxial wafer is shown.

[0030] Step 2: Photolithography process to form a mask:

[0031] In this embodiment, a photoresist S1818 was spin-coated on a coating machine at a speed of 1500 rpm and a pre-bake temperature of 110°C for 1 minute before exposure to obtain Figure 2 The epitaxial wafer shown in the figure is exposed to UV light using a SUSS MA6 lithography machine to transfer the photoresist pattern to the surface of the structure wafer with an exposure dose of 200Mj / cm2; the epitaxial wafer is developed at room temperature using an AZ 300MIF lithography machine for 1 minute, rinsed with deionized water and dried to obtain the epitaxial wafer. Figure 3 An epitaxial wafer with a photoresist mask is shown.

[0032] Step 3: Lightweight thermal reflow process:

[0033] The photoresist mask is processed using a lightweight thermal reflow process so that the edge of the photoresist mask forms an arc-shaped profile; according to the glass transition temperature range of the photoresist S1818, this embodiment bakes the developed epitaxial wafer at a baking temperature of 150° C. for 1 minute, so that the photoresist mask is thermally reflowed to form the following Figure 4 The edge is shown as curved.

[0034] Step 4: Dry etching:

[0035] The dielectric layer is etched using a dry etching process with an etching selectivity of 0.8 to 1.2 to form a dielectric pad layer structure with an arc-shaped edge profile, and the residual photoresist is removed. In this embodiment, a Samco etching device is used, the etching gas O2 / CF4=30sccm / 30sccm, the RF power is 80W, and the pressure is 5Pa. The etching rate of this etching program for the S1818 photoresist mask is ER pr=201nm / min, the etching rate for BCB is ER bcb=210nm / min, the etching selectivity is 1.04, and the etching time is 12min, resulting in the following: Figure 5 The BCB pad layer structure with an arc-shaped edge is shown in the figure; the structure piece is placed in an NMP cleaning tank and allowed to stand at room temperature for 15 minutes, transferred to a second cleaning tank and allowed to stand at room temperature for 15 minutes, and then transferred to an IPA tank and allowed to stand at room temperature for 5 minutes. Finally, it is rinsed with deionized water and dried, and the residual photoresist is completely removed, and the following is obtained: Figure 6 The edge of the BCB high-layer structure of the epitaxial wafer shown has a smooth arc-shaped contour.

[0036] right Figure 6 The epitaxial wafer shown is subjected to metal evaporation to form a PAD electrode. Since the edge of the BCB pad layer structure has a smooth arc-shaped contour, no evaporation metal fault problem will occur during the metal evaporation process, thereby effectively ensuring the continuity of metal evaporation at the contour edge and improving the performance and reliability of the semiconductor laser.

Claims

1. A method for preparing a semiconductor laser, comprising: The invention also includes a step of forming a dielectric spacer layer structure on the surface of the epitaxial substrate for reducing parasitic capacitance, and a step of evaporating a PAD electrode on the surface of the epitaxial substrate having the dielectric spacer layer structure formed thereon; the step of forming the dielectric spacer layer structure on the surface of the epitaxial substrate using the following process: S1, preparing a dielectric layer on the surface of the epitaxial substrate; S2, forming a photoresist mask on the surface of the dielectric layer; S3, treating the photoresist mask using a lightweight thermal reflow process with a processing temperature within the glass transition temperature range of the photoresist, so that the edge of the photoresist mask forms an arc-shaped profile; S4. Etching the dielectric layer using a dry etching process with an etching selectivity ratio of 0.8 to 1.2 to form a dielectric pad layer structure with an arc-shaped edge profile, and removing residual photoresist.

2. The method for preparing a semiconductor laser according to claim 1, wherein: The dielectric layer material is BCB, PI, or SiO.

3. The method for preparing a semiconductor laser according to claim 1, wherein: The processing temperature of the lightweight thermal reflow process is within the glass transition temperature range of the photoresist used, and the processing time is 5s to 70s.

4. A semiconductor laser, characterized in that It is prepared using the method according to any one of claims 1 to 3.

Images