Semiconductor laser preparation method and semiconductor laser

Abstract

The present application provides a method for preparing a semiconductor laser and a semiconductor laser, wherein the method comprises: preparing an alignment mark on a wafer to be processed, and preparing a ridge waveguide based on the alignment mark; preparing an electrode window after depositing an insulating dielectric film on the surface of an epitaxial material on which the ridge waveguide is prepared; performing shallow etching of a preset depth on the wafer on which the electrode window is prepared by a shallow etching process, and performing etching modification of a preset time on the wafer on which the shallow etching is completed by an etching modification process to obtain a target wafer; performing metal evaporation and metal electroplating on the target wafer to obtain a P-side electrode, and performing thinning and metal evaporation on the back side of the substrate of the target wafer on which the P-side electrode is prepared to form an N-side electrode, which can ensure the surface yield and test yield by shallow etching, eliminate the damage problem caused by etching of the electrode window, and eliminate the evaporation cavity problem caused by shallow etching by etching modification, thereby ensuring the reliability of the semiconductor laser device.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor laser preparation, and in particular to a semiconductor laser preparation method and a semiconductor laser. Background Art

[0002] For the semiconductor laser manufacturing process, various contamination defects may occur during the wafer taping process, leading to chip failure.

[0003] Currently, AOI (Automated Optical Inspection) is mostly used to screen out qualified products with good appearance. However, due to the accuracy limitation of automatic optical inspection equipment, smaller defects (i.e. defects whose size is smaller than the detection accuracy of the equipment) cannot be identified and are missed, affecting the reliability of the device. Summary of the invention

[0004] The present application provides a semiconductor laser preparation method and a semiconductor laser, which are used to solve the problem that the reliability of semiconductor laser devices cannot be guaranteed due to the accuracy limitation of automatic optical detection equipment.

[0005] In a first aspect, the present application provides a method for preparing a semiconductor laser, comprising:

[0006] preparing an alignment mark on a wafer to be processed, and preparing a ridge waveguide based on the alignment mark;

[0007] After depositing an insulating dielectric film on the surface of the epitaxial material on which the ridge waveguide is prepared, an electrode window is prepared;

[0008] The wafer on which the electrode window is prepared is shallowly etched to a preset depth by a shallow etching process, and the wafer on which the shallow etching is completed is etched for a preset time by an etching modification process to obtain a target wafer;

[0009] The target wafer is subjected to metal evaporation and metal electroplating to obtain a P-side electrode, and the back side of the substrate of the target wafer prepared with the P-side electrode is thinned and metal evaporated to form an N-side electrode.

[0010] According to a semiconductor laser manufacturing method provided by the present application, the preset depth is determined based on the size of a target defect in the electrode window.

[0011] According to a semiconductor laser manufacturing method provided by the present application, the preset depth is half the length of the short side of the target defect.

[0012] According to a method for preparing a semiconductor laser provided in the present application, the method further includes:

[0013] Obtaining a modification temperature for etching modification of a wafer that has completed a shallow etching process, a preset depth of shallow etching, and a target size of a silicon nitride layer;

[0014] determining a modification rate based on the modification temperature;

[0015] Determining the preset duration based on the modification rate, the preset depth, and the target size;

[0016] Wherein, the epitaxial material includes a silicon nitride layer, and the target size is a size of the silicon nitride layer exceeding the electrode window after shallow etching.

[0017] According to a semiconductor laser manufacturing method provided by the present application, the preset time length is determined based on the modification rate, the preset depth and the target size, including:

[0018] Based on the target size, determining the length of the short side of the target size;

[0019] Taking the minimum value of the short side length and the preset depth as the modified length;

[0020] The preset duration is determined based on the modification rate and the modification length.

[0021] According to a semiconductor laser manufacturing method provided by the present application, the preset time length is determined based on the modification rate, the preset depth and the target size, including:

[0022] Determine a lateral modification depth and a longitudinal modification depth corresponding to an etching modification process based on the preset depth and the target size;

[0023] Determine the lateral modification time and the longitudinal modification time based on the lateral modification depth, the longitudinal modification depth and the modification rate corresponding to the etching modification process;

[0024] The preset duration is determined based on the horizontal modification duration and the vertical modification duration; wherein the preset duration is the smaller value between the horizontal modification duration and the vertical modification duration.

[0025] According to a semiconductor laser preparation method provided by the present application, the etching solution corresponding to the etching modification process is a buffered oxide etching solution.

[0026] According to a semiconductor laser preparation method provided in the present application, the composition and ratio of the etching liquid corresponding to the shallow etching process are H2SO4:H2O2:H2O=1:1:30, and the etching temperature corresponding to the shallow etching process is 22°C.

[0027] According to a semiconductor laser manufacturing method provided in the present application, the target defect refers to particles located in the electrode window area whose size is smaller than the recognition accuracy of the automatic optical detection equipment.

[0028] In a second aspect, the present application also provides a semiconductor laser, which is prepared by the method described above.

[0029] The present application provides a semiconductor laser preparation method and a semiconductor laser, which are as follows: preparing an alignment mark on a wafer to be processed, and preparing a ridge waveguide based on the alignment mark; preparing an electrode window after depositing an insulating dielectric film on the surface of an epitaxial material on which the ridge waveguide is prepared; shallowly etching the wafer on which the electrode window is prepared to a preset depth through a shallow etching process, and etching and modifying the wafer on which the shallow etching is completed for a preset time through an etching modification process to obtain a target wafer; performing metal evaporation and metal electroplating on the target wafer to obtain a P-side electrode, and thinning and metal evaporating the back side of the substrate of the target wafer on which the P-side electrode is prepared to form an N-side electrode, and can use shallow etching to remove small particles that cannot be identified by AOI, thereby optimizing the surface yield. The surface particles that are not removed by shallow etching are large in size and can be identified by AOI and will not flow into the client, thereby ensuring the test yield. At the same time, shallow etching can also eliminate the damage problem caused by etching the electrode window, and etching modification can eliminate the evaporation cavity problem caused by shallow etching, thereby maximizing the reliability of the semiconductor laser device. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the present application or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 It is a schematic diagram of the process of preparing a semiconductor laser provided by the present application;

[0032] Figure 2 It is a schematic diagram of the process effect before preparing the electrode window provided in the present application;

[0033] Figure 3 It is a comparison diagram of the state before and after shallow corrosion provided by this application;

[0034] Figure 4 It is a schematic diagram of the process of determining the preset duration provided by this application;

[0035] Figure 5 This is one of the detailed flow charts provided in this application for determining the preset duration based on the modification rate, preset depth and target size;

[0036] Figure 6 This is the second detailed flow chart of determining the preset duration based on the modification rate, preset depth and target size provided in this application. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0038] Figure 1 is a schematic diagram of the process of preparing a semiconductor laser provided by the present application, such as Figure 1 As shown, including:

[0039] Step S1, preparing an alignment mark on a wafer to be processed, and preparing a ridge waveguide based on the alignment mark;

[0040] Step S2, preparing an electrode window after depositing an insulating dielectric film on the surface of the epitaxial material for preparing the ridge waveguide;

[0041] Step S3, performing shallow etching of a preset depth on the wafer on which the electrode window is prepared by a shallow etching process, and performing etching modification of a preset time on the wafer on which the shallow etching is completed by an etching modification process to obtain a target wafer;

[0042] Step S4, performing metal evaporation and metal electroplating on the target wafer to obtain a P-side electrode, and performing thinning and metal evaporation on the back side of the substrate of the target wafer prepared with the P-side electrode to form an N-side electrode.

[0043] Specifically, in step S1 and step S2, the steps of preparing alignment marks, preparing ridge waveguides, depositing insulating dielectric films and preparing electrode windows can all adopt existing conventional preparation methods, and the embodiments of the present application are not specifically limited here. Figure 2 Schematic diagram of the process effect before preparing the electrode window provided in this application, such as Figure 2 As shown, the first step corresponds to the effect after the preparation of the alignment mark and the non-pump area, the second and third steps correspond to the effect after the preparation of the ridge waveguide, and the fourth step corresponds to the effect after the deposition of the insulating dielectric film.

[0044] Based on the above content, it can be known that due to the precision limitation of the automatic optical inspection equipment, smaller defects cannot be identified and are missed, affecting the reliability of the device. The defects located in the electric injection area are the key factors affecting the reliability of the semiconductor laser. Therefore, before the metal evaporation of the electrode window, it is necessary to ensure that the electrode window is completely clean or the defects in the electrode window can be identified by AOI. In the actual production process, it is almost impossible to ensure complete cleanliness, so it can only rely on AOI identification; but relying only on AOI identification faces the precision limitation of the automatic optical inspection equipment. Therefore, the embodiment of the present application proposes a semiconductor laser preparation method for this problem, and its focus is on the above-mentioned step S3, that is, performing a shallow etching process and an etching modification process before metal evaporation. It can be understood that the above-mentioned defects mainly refer to particles on the surface of the wafer, including dirt and residues, and the shape of the defects may be a regular sphere or an irregular shape. For defects with smaller sizes, the automatic optical inspection equipment cannot identify them. Therefore, the embodiment of the present application uses a shallow etching process to etch the target defects. The target defect refers to particles located in the electrode window area whose size is smaller than the recognition accuracy of the automatic optical inspection equipment. It is understood that the recognition accuracy of the automatic optical inspection equipment is characterized by the minimum size of the defect that the AOI can identify. The size usually refers to the diameter or side length of the defect. For regular spherical particles, the diameter is used to characterize it, and for non-spherical particles, the side length is used to characterize it.

[0045] The composition and ratio of the etching liquid corresponding to the shallow etching process are preferably H2SO4:H2O2:H2O=1:1:30. The etching temperature corresponding to the shallow etching process needs to comprehensively consider the influence of the corrosion morphology, corrosion rate and process convenience. In the embodiment of the present application, the etching temperature corresponding to the shallow etching process is preferably 22°C. The preset depth is determined based on the size of the target defect in the electrode window. The embodiment of the present application determines the size distribution of the target defect through multiple tests in advance, and determines the defect with the largest size among the target defects, and then determines the preset depth corresponding to the shallow etching based on the relevant parameters of the defect with the largest size among the target defects. Based on this, it can be guaranteed to be fully corroded to the maximum extent.

[0046] Specifically, the preset depth is half the length of the short side of the target defect. It is understandable that, since the longitudinal and lateral rates corresponding to shallow corrosion are basically the same, for a defect of size a×b, the corrosion depth only needs to exceed min(a, b) / 2, that is, half the length of the shortest side of the defect size.

[0047] It is understandable that the final yield includes the surface yield and the test yield. The embodiment of the present application can remove small particles that cannot be recognized by AOI through shallow etching, thereby optimizing the surface yield. The surface particles that are not removed by shallow etching can be recognized by AOI due to their large size, so they will not flow into the client, thereby ensuring the test yield. Based on the above two points, the overall reliability of the semiconductor laser after shallow etching is higher. It is worth noting that for defects that were originally recognized by AOI but cannot be recognized by AOI after shallow etching, the embodiment of the present application circumvents this problem by performing AOI recognition after metal evaporation. The principle is that the original defect will be magnified after metal evaporation. For example, there is a 1um defect before metal evaporation, and the AOI recognition capability is 3um, which cannot be recognized. After metal evaporation, the defect will be enlarged to 3um and can be recognized.

[0048] It is also worth noting that before metal evaporation, the existing process method usually removes the oxide layer from the surface of the wafer, and the conventional method is to use HCl for treatment to remove the natural oxide layer on the surface. The embodiment of the present application uses shallow corrosion instead of HCl treatment, which can remove small particles on the surface of the wafer without increasing the process flow, and can further improve the final yield on the basis of ensuring the existing process effect. In addition, shallow corrosion before metal evaporation can also eliminate the damage problem caused by electrode window etching, and further improve the reliability of semiconductor lasers. Specifically, in the embodiment of the present application, the electrode window is obtained by reactive ion etching (ie, RIE). Although RIE has obvious advantages in dimensional accuracy, surface quality, uniformity and repeatability, the use of RIE to prepare the electrode window will cause plasma damage to the wafer, and the shallow corrosion process of the embodiment of the present application can just remove the damaged layer while etching the defect.

[0049] Although the shallow etching process of the embodiment of the present application has the above advantages, the present applicant has found through research that it will also cause certain negative effects, namely, metal evaporation holes. Figure 3 This is a comparison diagram of the state before and after shallow corrosion provided by this application, such as Figure 3 As shown, after the shallow etching process, lateral corrosion will occur under the SiN (silicon nitride) layer of the epitaxial material to form metal vapor-deposited holes. The metal vapor-deposited holes will affect the subsequent processes and also affect the heat dissipation of the chip. To address this problem, the embodiment of the present application further modifies the metal vapor-deposited holes through an etching modification process. Specifically, the etching solution corresponding to the etching modification process is a buffered oxide etching solution (i.e., BOE etching solution). On this basis, the embodiment of the present application also needs to determine the preset time length before performing the etching modification process. Specifically, Figure 4 This is a schematic diagram of the process of determining the preset duration provided by this application, such as Figure 4As shown, the method also includes:

[0050] Step 101, obtaining a modification temperature for performing etching modification on a wafer that has completed a shallow etching process, a preset depth of shallow etching, and a target size of a silicon nitride layer;

[0051] Step 102, determining a modification rate based on the modification temperature;

[0052] Step 103, determining the preset duration based on the modification rate, the preset depth and the target size;

[0053] Wherein, the epitaxial material includes a silicon nitride layer, and the target size is a size of the silicon nitride layer exceeding the electrode window after shallow etching.

[0054] It is understandable that the aforementioned metal evaporation holes are caused by lateral corrosion of shallow corrosion. Assuming the corrosion depth is 100nm, the lateral void size is also close to 100nm, that is, the SiN above the 100nm void needs to be removed. However, the corrosion time corresponding to the etching modification process should not be too long. Excessive corrosion time will form new voids at the interface between the epitaxial material and SiN. Therefore, it is necessary to comprehensively consider and select the appropriate corrosion time. Based on this, the embodiment of the present application first needs to obtain the modification temperature for etching modification of the wafer that has completed the shallow etching process, the preset depth of shallow etching, and the target size of the silicon nitride layer, and then determine the modification rate, and based on the modification rate, the preset depth and the target size, determine the preset duration. Combined with Figure 3 It can also be understood that the target size is the size of the electrode window that the silicon nitride layer exceeds after the shallow etching. It is worth noting that the modification temperature corresponding to the etching modification process is a preset value, the preset depth of the shallow etching is known, and the target size of the silicon nitride layer can also be quickly obtained through existing detection means. On this basis, the modification rate can be quickly determined based on the modification temperature, and then the preset time can be determined based on the modification rate, the preset depth and the target size.

[0055] Specifically, in the embodiment of the present application, based on the modification rate, the preset depth and the target size, the preset duration can be determined in two ways. Figure 5 This is one of the detailed flow charts provided in this application for determining the preset duration based on the modification rate, preset depth and target size, such as Figure 5 As shown, based on the modification rate, the preset depth and the target size, determining the preset duration includes:

[0056] Step 1031, based on the target size, determining the short side length of the target size;

[0057] Step 1033, taking the minimum value of the short side length and the preset depth as the modified length;

[0058] Step 1035: Determine the preset duration based on the modification rate and the modification length.

[0059] Based on the foregoing, it can be understood that, since the longitudinal and lateral rates corresponding to the etching process are substantially the same, similar to the method for determining the preset depth of the shallow etching process, the embodiment of the present application first needs to determine the shortest modification length, and then the preset duration (i.e., the quotient of the modification length and the modification rate) can be determined based on the modification rate and the modification length. For the method for determining the modification length, first determine the short side length of the target size based on the target size, and then compare the short side length with the preset depth, and the minimum value of the short side length and the preset depth is the modification length.

[0060] Figure 6 This is the second detailed flow chart of determining the preset duration based on the modification rate, preset depth and target size provided by the present application, such as Figure 6 As shown, based on the modification rate, the preset depth and the target size, determining the preset duration includes:

[0061] Step 1032, determining a lateral modification depth and a longitudinal modification depth corresponding to an etching modification process based on the preset depth and the target size;

[0062] Step 1034, determining a lateral modification time and a longitudinal modification time based on the lateral modification depth, the longitudinal modification depth and the modification rate corresponding to the etching modification process;

[0063] Step 1036, determining the preset duration based on the horizontal modification duration and the vertical modification duration; wherein the preset duration is the smaller value between the horizontal modification duration and the vertical modification duration.

[0064] Different from the first method mentioned above, which directly determines the shortest modification length and then determines the preset duration based on the modification length, the second method first determines the horizontal and vertical modification durations, and then determines the preset duration based on the horizontal and vertical modification durations. Specifically, the embodiment of the present application first determines the horizontal modification depth and vertical modification depth corresponding to the etching modification process based on the preset depth and the target size, and then determines the horizontal modification duration and vertical modification duration based on the horizontal modification depth and vertical modification depth corresponding to the etching modification process and the modification rate. It can be understood that the vertical modification depth is Figure 3 The modification depth in the up-down direction is Figure 3 The modification depth in the left and right directions is the length of the silicon nitride layer exceeding the electrode window after the shallow etching.

[0065] The preset time lengths obtained based on the above two methods can ensure that the etching modification can eliminate the evaporation void problem caused by shallow corrosion, thereby maximizing the reliability of the semiconductor laser device.

[0066] As for step S4, metal evaporation and metal thickening are performed on the target wafer to obtain a P-side electrode, and the back side of the substrate of the target wafer prepared with the P-side electrode is thinned and metal evaporated to form an N-side electrode. This is a conventional process step in the field, and the specific principles and processes will not be repeated in this embodiment of the present application.

[0067] The semiconductor laser preparation method provided in the embodiment of the present application comprises the following steps: preparing an alignment mark on a wafer to be processed, and preparing a ridge waveguide based on the alignment mark; preparing an electrode window after depositing an insulating dielectric film on the surface of an epitaxial material on which the ridge waveguide is prepared; performing shallow etching of a preset depth on the wafer on which the electrode window is prepared by a shallow etching process, and performing etching modification on the wafer on which the shallow etching is completed for a preset time by an etching modification process to obtain a target wafer; performing metal evaporation and metal electroplating on the target wafer to obtain a P-side electrode, and performing thinning and metal evaporation on the back side of the substrate of the target wafer on which the P-side electrode is prepared to form an N-side electrode. Shallow etching can be used to remove small particles that cannot be identified by AOI, thereby optimizing the surface yield. The surface particles that are not removed by shallow etching are relatively large in size and can be identified by AOI and will not flow into the client, thereby ensuring the test yield. At the same time, shallow etching can also eliminate the damage problem caused by etching of the electrode window, and etching modification can eliminate the evaporation void problem caused by shallow etching, thereby maximizing the reliability of the semiconductor laser device.

[0068] The present application also provides a semiconductor laser, which is prepared by the method described in any of the above embodiments.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a semiconductor laser, characterized in that: include: preparing an alignment mark on a wafer to be processed, and preparing a ridge waveguide based on the alignment mark; After depositing an insulating dielectric film on the surface of the epitaxial material on which the ridge waveguide is prepared, an electrode window is prepared; The wafer on which the electrode window is prepared is subjected to shallow etching at a preset depth by a shallow etching process to etch the target defect, and the wafer subjected to shallow etching is subjected to etching modification for a preset time by an etching modification process to obtain the target wafer; the target defect refers to particles located in the electrode window area whose size is smaller than the recognition accuracy of the automatic optical detection equipment; The target wafer is subjected to metal evaporation and metal electroplating to obtain a P-side electrode, and the back side of the substrate of the target wafer prepared with the P-side electrode is thinned and metal evaporated to form an N-side electrode.

2. The method for preparing a semiconductor laser according to claim 1, characterized in that: The preset depth is determined based on the size of the target defect of the electrode window.

3. The method for preparing a semiconductor laser according to claim 2, characterized in that: The preset depth is half of the length of the short side of the target defect.

4. The method for preparing a semiconductor laser according to any one of claims 1 to 3, characterized in that: The method further comprises: Obtaining a modification temperature for etching modification of a wafer that has completed a shallow etching process, a preset depth of shallow etching, and a target size of a silicon nitride layer; determining a modification rate based on the modification temperature; Determining the preset duration based on the modification rate, the preset depth, and the target size; Wherein, the epitaxial material includes a silicon nitride layer, and the target size is a size of the silicon nitride layer exceeding the electrode window after shallow etching.

5. The method for preparing a semiconductor laser according to claim 4, characterized in that: Determining the preset duration based on the modification rate, the preset depth, and the target size includes: Based on the target size, determining the length of the short side of the target size; Taking the minimum value of the short side length and the preset depth as the modified length; The preset duration is determined based on the modification rate and the modification length.

6. The method for preparing a semiconductor laser according to claim 4, characterized in that: Determining the preset duration based on the modification rate, the preset depth, and the target size includes: Determine a lateral modification depth and a longitudinal modification depth corresponding to an etching modification process based on the preset depth and the target size; Determine the lateral modification time and the longitudinal modification time based on the lateral modification depth, the longitudinal modification depth and the modification rate corresponding to the etching modification process; The preset duration is determined based on the horizontal modification duration and the vertical modification duration; wherein the preset duration is a smaller value between the horizontal modification duration and the vertical modification duration.

7. The method for preparing a semiconductor laser according to claim 5 or 6, characterized in that: The etching solution corresponding to the etching modification process is a buffered oxide etching solution.

8. The method for preparing a semiconductor laser according to claim 7, characterized in that: The composition and ratio of the etching solution corresponding to the shallow etching process are H2SO4:H2O2:H2O=1:1:30, and the etching temperature corresponding to the shallow etching process is 22°C.

9. A semiconductor laser, characterized in that: The method is prepared by the method according to any one of claims 1 to 8.

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