DFB LASER MANUFACTURING METHOD BASED ON DIELECTRIC LATERALLY COUPLED GRATING WITH DETERMINISTIC GRATING COUPLING COEFFICIENT

Abstract

The present invention discloses DFB laser manufacturing method based on dielectric laterally coupled grating with deterministic grating coupling coefficient, comprising: S1: performing photolithography on an epitaxial substrate of the laser without an etch-stop layer to obtain a photoresist pattern with a waveguide morphology in a predetermined geometric configuration, and then performing dry etching and removing the photoresist to obtain a substrate of a waveguide structure in the predetermined geometric configuration; S2: depositing a layer of an insulating film with a low refractive index on the substrate; S3: depositing a dielectric film with a high refractive index on the insulating film; S4: performing photolithography on the dielectric film to prepare a photoresist pattern as a laterally coupled grating morphology; S5: performing etching and removing the photoresist for the dielectric film on the photoresist pattern to prepare a dielectric laterally coupled grating for the laser, and to further prepare a DFB laser.

Claims

1. A DFB laser manufacturing method based on a dielectric laterally coupled grating with a deterministic grating coupling coefficient, wherein the DFB laser manufacturing method comprises steps of: S1: performing photolithography on an epitaxial substrate of a laser without an etch-stop layer to obtain a photoresist pattern with a waveguide morphology in a predetermined geometric configuration, and then performing dry etching and removing a photoresist to obtain a substrate of a waveguide structure in the predetermined geometric configuration; S2: depositing a layer of an insulating film with a low refractive index on the substrate obtained in the step S1; S3: depositing a dielectric film with a high refractive index on the layer of the insulating film; S4: performing photolithography on the dielectric film to prepare a photoresist pattern with a laterally coupled grating morphology; S5: performing etching and removing the photoresist for the dielectric film on the photoresist pattern obtained in the step S4 to prepare a dielectric laterally coupled grating for the laser, and using the dielectric laterally coupled grating to prepare a DFB laser.

2. The DFB laser manufacturing method based on the dielectric laterally coupled grating with the deterministic grating coupling coefficient according to claim 1, wherein the substrate of the waveguide structure in the predetermined geometric configuration obtained in the step S1 by performing dry etching and removing the photoresist is a zero-footing substrate of the waveguide structure with a deterministic geometry size, the predetermined geometric configuration is a positive trapezoid, the waveguide structure for the substrate of the waveguide structure in the predetermined geometric configuration has the positive trapezoid with an inner angle of 60° to 85°, the inner angle being favorable for a footing with a height of less than 100 nm.

3. The DFB laser manufacturing method based on the dielectric laterally coupled grating with the deterministic grating coupling coefficient according to claim 1, wherein a specific process of the step S1 comprises: performing photolithography on the epitaxial substrate of the laser without the etch-stop layer, and obtaining the photoresist pattern with the waveguide morphology in the predetermined geometric configuration by controlling exposure process or post-processing method, and then performing dry etching and removing the photoresist to obtain a zero-footing substrate of the waveguide structure in the predetermined geometric configuration with a determinable size.

4. The DFB laser manufacturing method based on the dielectric laterally coupled grating with the deterministic grating coupling coefficient according to claim 1, wherein the laser epitaxial substrate without the etch-stop layer in the step S1 comprises GaAs-based, GaSb-based and GaN laser materials.

5. The DFB laser manufacturing method based on the dielectric laterally coupled grating with the deterministic grating coupling coefficient according to claim 1, wherein an angle of the photoresist pattern with the waveguide morphology in the predetermined geometric configuration is ranged from 60° to 80°, and controlling exposure process parameters and post-processing methods comprises exposure dose, developing time, post-baking reflow or plasma dry processing.

6. The DFB laser manufacturing method based on the dielectric laterally coupled grating with the deterministic grating coupling coefficient according to claim 1, wherein, process parameters of the dry etching comprise process gas flow rate, pressure, plasma concentration, bias pressure or sample temperature.

7. The DFB laser manufacturing method based on the dielectric laterally coupled grating with the deterministic grating coupling coefficient according to claim 1, wherein the insulating film deposited in the step S2 has a thickness of less than 50 nm, the insulating film deposited is a dielectric material with a low refractive index, and the dielectric material with the low refractive index has a refractive index of less than 2.

8. The DFB laser manufacturing method based on the dielectric laterally coupled grating with the deterministic grating coupling coefficient according to claim 1, wherein the dielectric film deposited in the step S3 has a thickness of less than 300 mm, the deposited dielectric film is a high refractive index dielectric material, and the dielectric material with the high refractive index has a refractive index of greater than 2.

9. The DFB laser manufacturing method based on the dielectric laterally coupled grating with the deterministic grating coupling coefficient according to claim 1, wherein a grating design in the step S4 comprises correction of a grating period, duty cycle, grating length, and ridge waveguide position grating size, debugging exposure process comprises overall exposure dose debugging and local dose optimization.

10. The DFB laser manufacturing method based on the dielectric laterally coupled grating with the deterministic grating coupling coefficient according to claim 1, is wherein the dielectric laterally coupled grating prepared in the step S5 is a first-order or third-order grating.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0031] FIG. 1 is a schematic diagram of the structure of the LC-DFB laser with a deterministic grating coupling coefficient of the present invention.

[0032] FIG. 2 is a flow chart of a LC-DFB laser manufacturing method based on a deterministic grating coupling coefficient of a dielectric laterally coupled grating of the present invention.

[0033] FIG. 3 is the SEM diagram of a low-footing and positive trapezoid tilted waveguide structure covered with photoresist of an embodiment of the present invention.

[0034] FIG. 4 is the SEM diagram of a photoresist pattern with a laterally coupled grating morphology of an embodiment of the present invention.

[0035] FIG. 5 is the SEM diagram of the structure of a DFB laser dielectric grating (take amorphous silicon for example) obtained by an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0036] To facilitate a more comprehensive comprehension of the aforementioned objectives, characteristics, and benefits of the present invention, the invention is elaborated further below in conjunction with the associated drawings and specific examples. It is noteworthy that the embodiments and features disclosed in this application may be integrated with one another as long as there is no contradiction between them.

[0037] Although many specific details are set forth in the following description in order to facilitate a full understanding of the invention, the invention may also be implemented in other ways than those described herein, and therefore the scope of protection of the invention is not limited by the specific embodiments disclosed below.

Embodiment 1

[0038] As shown in FIG. 1, a DFB laser manufacturing method based on a deterministic grating coupling coefficient of a dielectric laterally coupled grating, comprising the following steps:

[0039] S1: performing photolithography on an epitaxial substrate of the laser without an etch-stop layer to obtain a photoresist pattern with a waveguide morphology in a predetermined geometric configuration. The photoresist pattern is then used as a mask for dry etching, which removes the unprotected regions of the substrate, resulting in a substrate of a waveguide structure in the predetermined geometric configuration, as illustrated in FIG. 3.

[0040] It should be noted that in a specific embodiment, the predetermined geometric configuration of the waveguide can be a positive trapezoid. The process involves photolithography on the epitaxial substrate of the laser without the etch-stop layer to obtain a photoresist pattern with a waveguide morphology in a positive trapezoid configuration by controlling the exposure process or post-processing method. Then, dry etching is performed to remove the photoresist and obtain a zero-footing substrate of the waveguide structure in the predetermined geometric configuration with a determinable size. This zero-footing waveguide structure can be used for accurate estimation of the grating coupling coefficient of the DFB laser, as depicted in FIG. 3.

[0041] It should be noted that the zero-footing waveguide structure is obtained by designing the waveguide structure with a positive trapezoid configuration. The determinable size of the zero-footing waveguide structure facilitates accurate estimation of the grating coupling coefficient of the DFB laser and enables the determination of the interaction of the grating with the optical field in the active region.

[0042] The epitaxial substrate of the laser without the etch-stop layer in step S1 includes GaAs-based, GaSb-based and GaN laser materials. The etching cannot be accurately stopped over the active region in etching due to the presence of Al elements in the separate confinement layer.

[0043] Further, the angle of the photoresist pattern with the waveguide morphology in the predetermined geometric configuration is ranged from 60° to 80°, and controlling exposure process parameters and post-processing methods including exposure dose, developing time, post-baking reflow or plasma dry processing.

[0044] The waveguide structure for the substrate of the waveguide structure in the predetermined geometric configuration has the positive trapezoid with an inner angle of 60° to 85°, and the inner angle is favorable for corner footing with a height of less than 100 nm while facilitating a more accurate estimation of the grating coupling coefficient.

[0045] Further, process parameters of the dry etching comprise process gas flow rate, pressure, plasma concentration, bias pressure magnitude or sample temperature.

[0046] S2: a layer of an insulating film with a low refractive index is deposited on the substrate obtained in the step S1.

[0047] It should be noted that the insulating film deposited in this step has a thickness of less than 50 mm and consists of a low refractive index dielectric material (n<2, where n is the refractive index of the low refractive index dielectric material). This facilitates the coupling of the grating with the optical field in the active region and enables easier refractive index modulation.

[0048] S3: a dielectric film with a high refractive index is deposited on the layer of the insulating film.

[0049] It should be noted that the dielectric film deposited in the step S3 has a thickness of less than 300 mm. The deposited dielectric film is a high refractive index dielectric material, such as amorphous silicon, silicon nitride rich, etc. And the dielectric material with the high refractive index has a refractive index of greater than 2.

[0050] The present invention improves the preparation accuracy of the process and circumvents the absorption loss introduced by the metal grating, through the introduction of high refractive index dielectric materials (such as amorphous silicon, silicon nitride rich, etc.).

[0051] S4: photolithography is performed on the dielectric film to prepare a photoresist pattern with a laterally coupled grating morphology, as shown in FIG. 4.

[0052] The grating design includes correction of the grating period, duty cycle, grating length, and ridge waveguide position grating size. Debugging exposure process comprises overall exposure dose debugging and local dose optimization.

[0053] S5: etching and removing the photoresist for the dielectric film are performed on the photoresist pattern obtained in the step S4 to prepare a dielectric laterally coupled grating for the laser, and using the dielectric laterally coupled grating to prepare a DFB laser, as shown in FIG. 5.

[0054] The amorphous silicon grating prepared in step S5 is a first-order or third-order grating. Since the size of the waveguide can be determined, the size of the dielectric grating can be determined, so that the laser device with a deterministic grating coupling coefficient can be prepared. In one specific embodiment, the obtained dielectric laterally coupled grating can be used to prepare the DFB laser by using the existing process flow. The existing process flow includes planarization, P-type electrode preparation, substrate thinning, N-type electrode preparation, and annealing to form ohmic contacts.

[0055] The dielectric laterally coupled grating proposed by the invention is formed by etching, which can obtain high-quality, fine and stable first-order and third-order gratings and can achieve ultra-small grating period intervals (adjacent wavelength grating feature size is less than 2 nm).

[0056] The invention realizes the high repeatability preparation of laterally coupled gratings of laser epitaxial materials (GaAs, GaSb, GaN-based) without the etch-stop layer, and realizes DFB lasers with deterministic grating coupling coefficients, which further improves the flexibility of DFB laser array design and facilitates the utilization of epitaxial wafers and the realization of multi-wavelength arrays.

[0057] Obviously, the above embodiments of the present invention are only for the purpose of clearly explaining the examples of the present invention, but not for the purpose of limiting the protection scope of the present invention. For those skilled in the art, other changes or variations in different forms can be made on the basis of the above description. It is unnecessary and impossible to enumerate all the implementation methods here. Any modification, equivalent substitution or improvement made within the spirit and principle of the invention shall fall within the protection scope of the claims of the present invention. cm What is claimed is: